Go for a prepaid provider and give out as little personal information as necessary. Avoid the major carriers directly because they need a social security number.
That said, mobile phones are inherently not private. No matter what provider you choose, they will be able to track your location using tower triangulation. Even if you give a fake address, it would be pretty easy to identify you if you always have your phone on at home.
The official client has, but Syncthing-Fork is still being developed.
Same. It may lack encryption that many look for, but I have accepted that email is too old to ever be truly secure. Most email is either coming from, or going to services provided by big tech companies anyway. I prefer an open, fully standards compliant email service over a locked down service that provides minimal additional security.
I agree that Kagi isn’t great from a privacy perspective. But in regards to clearing cookies, they do have a session link feature that uses a token to avoid the need to sign in all the time.
I do not know when you last tested Filen, but all of those work for me. They had a major update several months ago with a rebuilt desktop app and added the virtual drive functionality.