I'm using Graphene. The Pixel requirement I believe is due to the Titan chip: https://security.googleblog.com/2021/10/pixel-6-setting-new-standard-for-mobile.html?m=1.
https://divestos.org/ has caught my eye. When I last installed Grapheme, you had to install eSIMs using the factory ROM then install Graphene. Divest I guess had support without Google services. I think Grapheme does now also, but before I get my next phone I'll weigh it as an option.