Since T403510: [Main Rollout] Enable unified mobile routing on remaining wikis rolled out to wikimedia.org wikis on 29 September, we've noticed some page loads on donate.wikimedia.org are now using Minerva. What's strange is that it doesn't seem to depend on desktop/mobile device, sometimes it loads Minerva on desktop browsers and I haven't been able to identify any pattern as to why. It seems like mobilefrontend is unintentionally enabled there.
I patched the onwiki CSS to fix the main issues with Minerva, so it's now functional for donors. But it does result in some inconsistencies in appearance depending on which skin is shown.
We should disable mobilefrontend on donatewiki so that it goes back to the old behaviour of always showing Vector Legacy. This was the case before the recent deployment, since donatewiki never had a mobile subdomain. @Jdlrobson has requested we not move to Vector 2022 at this point.
(I also checked fundraising's thankyouwiki, and that already has mobilefrontend disabled)