It's not quite ready for the prime time, but there are some open source phones in the works. The two most notable are the Librem 5 (https://puri.sm/products/librem-5-usa/) and the Pinephone (https://www.pine64.org/pinephone/).

Flip phone. People laugh at mine, whatever. Honestly though I use a flip because it does what I need and it's tough as nails.

De-Googled android distros are definitely out there, but I also think flip phone plus small portable laptop is a very powerful combo.

Which self-hosting software do you recommend?

I'm self hosting Ghost for blogging, Home Assistant for smart home controller, and in the middle of setting up Vaultwarden for passwords. I also run a lot of stuff off my Synology - Synology Drive instead of Dropbox or Google Drive, Synology Photos instead of Google Photos. I don't have a great solution for email or phone - emails is paid hosting through Zoho and use Android for phone. I'd like to get off those. It's all a long drawn out process.