After rebasing my Flow upgrade stack, I noticed a bunch of new errors: https://gist.github.com/Ashoat/b83564168fda704b2ce9d8051d0f472e
I played around a bit and it seems like an incompatibility between CryptoKey and SubtleCrypto$JsonWebKey introduced in D9535 and D9661, here and here.
@marcin's proposed this solution, which addresses the issue by avoiding calling localforage.getItem in a situation where the type param is ambiguous.
Depends on D9786