the following is from the arch wiki ... https://wiki.archlinux.org/title/Steam/Troubleshooting#Other_issues

9.4 Text is corrupt or missing

Try installing lib32-fontconfig, ttf-liberation and wqy-zenhei (for Asian characters), then restart Steam to see whether the problem is solved.

Note:

Steam for Linux does not follow system-level font configurations.[6] Thus, modify user-level configuration if you want change fontconfig for steam.

When Steam cannot find the Arial font, font-config likes to fall back onto the Helvetica bitmap font. Steam does not render this and possibly other bitmap fonts correctly, so either removing problematic fonts or disabling bitmap fonts will most likely fix the issue without installing the Arial or ArialBold fonts. The font being used in place of Arial can be found with the command:

Thanks, I'll install that and see what happens the next time Steam updates.