This is a nice addition to their suite of offers. But I am currently using Aegis on Android, which works really well and is also FOSS. So I have no real reason to switch at this point.
also aegis needs next to no permissions(Camera for qr codes), bitwarden does need Network and some more
Bitwarden is my current password manager. If I want to get on this, would I have to redo all my passwords or what?
No.
What’s the advantage of this new app over TOTP in old bitwarden? (Except that this new one is free)
It’s separate, bundling your tokens into your password manager is not exactly great security and sort of defeats the whole purpose. As now if your password manager is somehow compromised so are your tokens.
With a separate app that should be using a different master password from your password manager it helps mitigate that risk you would now need to lose control of both
