can confirm, I’m running GrapheneOS right now with F-Droid and some extra repos as my only app store, it works fine for me. but I don’t use banking apps (web browsers do fine for that), and I’m using a de-Firebase-d version of Signal (Molly F-Droid) so no issues so far with no GMS and no SafetyNet.

edit: I should add that a new GrapheneOS update just released, this is in the release notes:

• disable anti-competitive code being injected by the Play Store into apps choosing to enable “App integrity > Automatic protection” when there’s a valid Play Store source stamp signature (proving that it’s an unmodified app from the Play Store, so we aren’t disabling an integrity check) since it prevents using the apps on GrapheneOS when apps also choose to enable “App integrity > Store listing visibility” with either the “Device integrity checks” or “Strong integrity checks” values enforcing having a device licensing Google Mobile Services and running the stock OS (circumventing this is protected by the DMCA exemption for jailbreaking)

so it looks like the devs are actively working around this issue and making changes to allow those checks to pass even without the ROM licensing GMS.