Hmm ... there would be the Mullvad Browser. It is Firefox-based, privacy orientated and comes from the Mullvad VPN Developers. So, it has a Company Background; I don't know if this is a negative Point for You.
The good Thing is, that they have a normal Repo what You can add. It is describted here:
Besides that, I would be out of good Ideas. Other Stuff I wouldn't see as a good Suggestion. But here are more that enough Users and I'm sure they can offer more Suggestions.