Contex: I installed GrapheneOS for the first time yesterday and I am trying to get my device setup.

I want to install and keep up to date apps on GOS. I have 2 users, one for most things that do not need Google playprotect (or whatever) and another user where I can use google sandboxed for things like banking apps.

I want to keep my degoogled user degoogled. What would you suggest to install apps such as Signal, Spotify, Here wego, and others?

Are APKMirror, Aptoide, APK pure or Taptap secure and reliable?

I am already using fdroid, acrescent and obtainium for whatever I can find, but not all apps seem to be available this way.