F-Droid is an installable catalogue of FOSS (Free and Open Source Software) applications for the Android platform. The client makes it easy to browse, install, and keep track of updates on your device.
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I think most apps are 64 bit now. It looks like you can check on F Droid by looking at the information for each app that shows the build type:
EDIT
My understanding is that if you don't see anything like that above, then the app is purely Java and doesn't contain any native binary libraries. That should mean that it would work on any phone.
K tx 4 reply.
This link is targeted mostly for developers: https://developer.android.com/google/play/requirements/64-bit#:~:text=Look%20within%20the%20lib%20folder,you%20have%2032%2Dbit%20libraries.
But 32 vs 64 bit really only affects apps running native code. Most game engines already support x64 so I would hope games are already compliant, unless they haven't been updated in the last 4-5+ years. Other apps that just use the NDK or otherwise are running native code could be a problem but I would assume that there's x64 support for most of their dependencies so they should be fine. They might have to just push a new update but I suspect that they already added support for x64 awhile ago.
If you're a bit tech savvy though, you could download Android Studio and follow that guide in the link to analyze any APK and verify that a given app will still work before upgrading to 14. You obviously won't be able to covert it to x64 but you can at least see what architectures any given app supports.