Security for a full blown web app is not trivial and has a bigger “attack surface” than a kdbx file moving p2p through my devices via syncthing.

Absolutely.

My Vaultwarden instance is only accessible via LAN or VPN though, I don’t think I’d want to expose it to the internet.

If that works for you, great. But a self-hosted service offers a lot of convenience for a relatively small amount of added risk. Some things I like about Bitwarden/Vaultwarden:

• can share logins easily w/ my wife, while each having our own passwords
• nice UX for my phone and desktop (prompts for most apps that require passwords)
• web vault so I can access my logins if I don’t have my phone with me (e.g. lost phone while traveling)

And since it’s self-hosted, I’m far less likely to be targeted than the official Bitwarden instance since an attacker would need to know my domain, as well as being able to exploit the vulnerability through my multiple layers (requests go through HAProxy, my VPN, and Caddy before getting to Vaultwarden). I can make it even more secure by putting it inside my VPN (I have mine routed outside my VPN for the web vault access).

Explain how can you use KeePass+Syncthing with 10-50 people (possibly different groups for different passwords) having different sets of access level while maintaining sane ease of use?

The passwords are encrypted in the first place so the security for them is only on the client side.

syncthing also relies on a web server for device discovery, it’s just that you’re probably using someone else’s server instead of hosting your own.

Correct me if I’m wrong, but I also think that Vaultwarden itself doesn’t have access to the unencrypted password database. In that sense it’s E2EE similar to KeePass, the only difference being that KeePass is a desktop app and Vaultwarden a web app.

Good for you man, I mean it. I would also use Keepass, but I share a lot of logins with my wife, and some with my kids, so having a self-hosted app that can sync seamlessly without added friction, like Bitwarden, is the next best thing.

I might try vaultwarden myself, given that my life partner is always asking me for some platform password I already shared. Is possible to use just on LAN to sync and keep using the passwords from the android client while out of reach? I was just reading about 30-days sessions in the docs. Apparently, yes. That’s huge (for me, I’d like not to expose anything, even with VPN)