The 64 bit requirement is only relevant to libraries such as SQLCipher which include native binaries. There are very few such libraries. They will need to be updated to include a 64 bit binary.
Edit: latest version of SQLCipher includes a 64 bit binary.
Yes, searched, there is no defined list of such libraries.
I got this final conclusion:
Rename your apk to zip & extract it, then search for any .so files inside, if you got anyone, just update that libraries to the latest that support 64bit.