You generally don’t need sudo to install flatpaks and actually pretty sure they advise against it.

The only superior Linux distro and DE is the one that works for you and meets your needs.

This is different for each user and, frankly, the joy of Linux that it has such a variety as to be able to meet almost everyone’s needs.

For me , personally, thats Debian/Gnome with minimal tweaks but just because it works for my workflow does not make it superior.

You could try https://2fas.com/ open source mobile application with browser extensions and cloud sync for backups.

Or www.bitwarden.com password manager is also open source and for a small “premium” supports 2FA for mobile/desktop/browser.