No database. No background processes

So it’s no IAM.

As /e/ and iodé depend on Lineage, there would be no difference. Only Graphene (Pixel-only) and Calyx (critical) are directly based on AOSP and could thus make a difference

Lineage covers many devices but is not very privacy friendly. It does not include Google integration by default. The ßain advantage is longer software support.

Graphene is most secure and privacy friendly OS and comes with support for sandboxed GApps (optional). Unfortunately it is only made for Google Pixel devices so I’m out.

Depending on your reasons and device you could also check alternatives like /e/.

Messages are not end to end encrypted and can thus be read from service provider.

Additionally Google is integrated into website.

And:

I was searching for any native(non-proxied) YouTube client for Android in kotlin.

No. It’s not. Please take a look at different licenses in this area, whatever ‘libre’ means

Saying “it sucks that they decided” sounds like blaming these users.

DivestOS developer who is maintainer for Mull and Fennec as well.