It doesn’t kill the point of 2fa. It’s something you have… you have your device. If you didn’t you wouldn’t have the TOTP code.
The something you know (password) is much more likely to be breached and stolen. That is what isn’t tied to your device. You probably want the second factor to be linked to just the devices you have.
I use KeepPassXC for desktop totp codes. I’m sure there’s an Android app to use with it. (I use KeePassium on iOS). Edit: maybe look into KeePass2Android
You can sync with Syncthing for offline. I keep the database in the cloud but with a key on each device (not in the cloud) that’s needed to open it.
Yep you can download a native app that has a bit more features than the web app.