I so far have been disappointed because some of the main things I I shall and had are a browser and password manager and they can’t talk to each other and flatpak refuses to fix it.
This is by design iirc, as a consequence of sandboxing. However there is an easy workaround, which is redirecting your browser profile back to the host with flatpak override/flatseal. I don't need this anymore for Bitwarden but I did this for a long time with Firefox + Enpass.
So is the iPhone and they provided ways to make it work. It’s a use case that is needed so they should be trying to find a (secure) way to do it.