I was surprised I haven’t seen this mentioned or discussed much before.
This is the Keybase alternative. Open source and decentralized. It also hosts no data and is basically just a frontend that pulls and presents your information hosted elsewhere (i.e. key servers) in one identity/profile page.
Here is the link and it’s very interesting, including all of the documentation: https://keyoxide.org
All code is hosted on Codeberg and it has an official app on F-Droid.
I wouldn’t say it’s difficult at all if you follow the guides and have some technical or GPG knowledge (I’m no GPG expert and setting up was smooth by following the guides), although the non-straightforward setup is something the project and author acknowledges and aims to simplify.
Keybase uses PGP as well and this is simply for evaluation as an alternative.
‘Passport’ is only a fancy term. Essentially it’s just an effective digital proof system which can even be as simple as proven.lol rather than using any cryptography, and Keyoxide uses GPG well to achieve this purpose.