After the recent giveaway of Rising Storm 2: Vietnam on Epic Store, I have noticed several posts asking how to play Talvisota - Winter War mod with the Epic version of RS2. The only "official" way of getting this mod is to install the distribution available on Steam, but obviously you need to purchase RS2 on Steam to do that. But there is a workaround for playing this glorious mod with the Epic version!
I created this guide for those who do not own RS2 on Steam but on Epic Store and wish to play Winter War. It´s actually really simple, just not obvious enough. In this guide I will help you to get your chance on experiencing this specific, harsh conflict, which Winter War mod depicts so accurately, for yourself! Just follow these simple steps.

Every player wanting to get into the Winter War needs first to realize that, althought made very professionally, it is a fan-made mod. That means that it can´t be whitelisted (though developers of RS2 were speaking about adding a feature for whitelisting in a future update) and that means the mod can´t be played as ranked. That again means that you can´t earn XP and level up playing this mod. One would think that in a game where leveling up can only earn you some cosmetic customization, this wouldn´t be an issue. But sadly it looks like many people care about that, and that is one of the reasons why this mod has not so many players anymore. But that doesn´t mean the mod is dead. And you are the one needed to keep it that way!
From what I know there is only one server in RS2 where this mod is always enabled. It is a Finnish server called "[fll.fi] Komppania Törni #3". Here is a link to a webpage where you can check status of the server, players currently online and other useful stuff:
https://www.battlemetrics.com/servers/rs2vietnam/3944284
Please note that for some reason the server can´t be found in the server browser occasionally, although the Battlemetrics page indicates it´s status is online. It happens mostly when there are no players on the server. Refreshing doesn´t help. I don´t know any fix for that except waiting a while for it to reappear.
There are also 3 other servers that have Winter War mod enabled occasionally ("[fll.fi] Komppania Törni #1", "[fll.fi] Komppania Törni #2" and "[fll.fi] Komppania Törni #4"), but numbers #1 and #4 are not online so often and #2 plays mostly vanilla RS2, so I recommend sticking to #3.
With that being said, let´s get into how you can utilize this intel to get on the battlefield!

This is it, boys. First, make sure that you have installed the Epic version of Rising Storm 2 and have all the updates. Please note that this method uses only Epic Launcher to get the mod, so don´t try to install Winter War mod through Steam with Epic version of RS2 - it won´t work. Launch RS2 and go into the server browser. There you need to locate the aforementioned server "[fll.fi] Komppania Törni #3". If you can´t find it, try to search by map, the server should be at the very bottom of the list. If you still can´t find it, you are probably experiencing the problem with the server disappearing from the server browser mentioned in the previous section. In that case just wait few hours and then try to search for it again. When you find it, I recommend favoriting it immediately to not have to search for it again. Please note that when you favorite it and then can´t find it between your favorites, you are experiencing the server disappearing from the server browser again. It will reappear in your favorites after some time too.

You made it this far, but the battle is only just about to start. Now you need a weapon - specifically a fast internet connection. Double click on the server to join it. Now here´s what will happen: you won´t be able to play the mod right away because you don´t own it yet. Instead, the server will start to feed you the mod as if you would be joining a custom map in RS2! You will see the normal RS2 downloading screen with the specific file that is being downloaded. Be aware that the mod will not download as a complete package. Rather, all the models and assets will be dowloaded piece by piece. That also means that in the initial dowload you will only get the most necessary files that allow you enter the game on the particular map which is played on the server in that moment. This means that at first you will get only portion of the mod including character models, some weapons, one map and all the assets that specific map requires. The initial download can still take some time so don´t interrupt the download and wait patiently! If your weapon (err, I mean internet connection) is not fast enough, the connection to the server may time out, the download will be cancelled and you will return to the server browser. But don´t worry, all the files downloaded to this point are saved. You just need to connect to the server again for the download to recommence.

Alright, soldier! Your initial download is finished and after waiting through standard RS2 loading screen you have been thrown into unfamiliar snowy battlefield! At least the menu seems familiar - actually it does not change at all from vanilla RS2. After selecting a team between Finnish and Soviet forces (that may still be named Vietcong & US Army, but with different flags), you can see the first difference: totally new classes and weapons. Select your role and jump into the fray. The Finnish SMG looks sweet, let´s take look at the secondary equipment. There´s the grenade... wait, what´s that error message? I don´t have all the assets that host has?! Kicked from the server... AAAAAAAAAAAAAAH!!

You just experienced defeat for the first time... but not by the enemy. As I mentioned earlier, the grenade model, as well as some other assets, are not necessary for you to load into the map, so the server let you in. Upon selecting the missing weapon it "realized" you don´t have all the files and kicked you. Again, don´t worry, because the very next time you connect to the server, the game will proceed to download the missing asset. Just be patient, because this can happen several times with other assets too, before your download of the Winter War mod is finally complete and you can enjoy the game without interruptions. For example, all the vehicle models will not be downloaded before you connect to a map that supports vehicles for the first time. Also every time you try to connect to a specific map for the first time, the whole map will be downloaded, so be prepared for that.

That´s all, soldier. I hope you will enjoy this great mod. Again remember that the mod is not vastly populated. But there are bots to solve the problem! All the Winter War maps support AI bots and they are on by default, so you can enjoy playing even without other players. The bots are gradually kicked as players join the server.
In the end I would like to stress out one thing that I already mentioned in the introduction. This is an "unofficial" method of getting the Winter War mod, because it has never been stated by the devs to be even possible to play it through Epic, and no one has ever answered to the topics asking how to play Winter War on the Epic version. This means that this method, although it works almost flawlessly, has also a few downsides.
Firstly, the modular structure of the download, with assets directly replacing RS2 files for the mod, causes some of the original names of the vanilla RS2 assets to be listed instead. I already mentioned how in menu the teams are still named Vietcong and US Army. Also sometimes when you want to pick up a weapon lying on the ground, it uses the vanilla name of the asset the mod replaced. Yeah, I found the M16 assault rifle in the snow! Oh, it´s only a Soviet grenade with wrong description... But this is really not an issue.
A far bigger downside of getting the mod using this method is that for some reason, the beautiful and very professional voice acting is missing for both Finns and the Soviet Union! The soldiers are totally mute and do not even scream when wounded. This is really an issue as the voice acting that works fine in the Steam version adds so much to the atmosphere. I didn´t find a solution for this problem. If you do, be sure to let everyone know!
There is also a new problem introduced by update 1.2.1 of the Winter War mod. If you have downloaded the mod before the update and you try to connect to one of the Winter War servers after the update, you get an error message saying you have some content that is out-of-sync with the server. You can´t join because apparently the updated files do not get re-downloaded automatically. But if you are downloading Winter War mod after the update, you should be fine. At least until the next update, that is.
There is some talk about devs working on a new launcher for the mod specifically aimed at enhancing the experience of Epic players by providing the full experience without all the aforementioned problems and with enabled voice acting. That would be great as it would make the experience of an Epic player equivalent to the one of a Steam player. But it was never stated in the official news and no release date for the launcher was provided. We can just hope this will happen.
This concludes my guide. Using Steam version is currently still the preferred method of playing this mod as it comes without these issues, but the mod is totally playable downloaded via Epic Launcher too. And as the vanilla RS2, Winter War obviously supports cross-play between Epic and Steam.

Over and out!