Reddit’s privately owned so no. :)

If something is on the internet and not encrypted, it’s public not private. Though you can at least be anonymous.

Even if no trackers (which there are) Lemmy is federated so you cannot just delete your stuff and sleep over it. However if you need to be careful, you can solely use Lemmy over Tor. It’s not private but can be anonymous.

I think I recently read that Lemmy devs are working on private upvotes / downvotes (yes even they can be tracked) but it seems it’s tricky with federation.

So, generally Fediverse is not private and cannot be private due to its nature. If you have a threat model, you should use it with Tor.

I have a similar setup with LineageOS. I use KeePassXC on PC (KeePassDX on Android). I can sync them via Nextcloud with peace in mind because the database is already encrypted. Syncthing-fork also works if you want completely local.

I’m sure e/OS already has a password vault app in their list but if not KeePassXC is fully local out of the box and can be used with DX on Android.

It’s far secure than Firefox’s built-in password manager.

You can use local ones like KeePassXC.