h0rs3m4n if you're using the built in GOS phone app, I'm not aware of any app options to block spam on Accrescent or F-Droid but if you're ok with google having access to your calls you could always download google phone from the google play store and the configure any of the usual apps to work with that. I imagine you would just have to give it unrestricted battery access and all the phone related permissions.
If you don't like the idea of using google phone just like I don't, I can personally recommend using a service like delete me or incogni. That reduced the number of spam calls I got, plus there's the peace of mind knowing my data isn't all out there.
For 2FA apps, google authenticator works well with GOS, no issues. But I would imagine Aegis works just as well and it's open source