Sourcehut has accepted no external funding and once the alpha period ends, all accounts must be paid. Even with optional payment, it already turns a profit. I'm pretty confident in the sustainability of the service.
As for me losing interest, the good news is that I need software hosting no matter what I'm working on, so I'll always be working on it. And, since it's open source and patches are welcome, so could you add anything you need.
You just got another paid user. I am very much in the amateur hacker camp, so I might not add much revenue. Anyway, thanks for sourcehut. Mercurial is my preferred way. I have managed to shoot myself in the foot so many times with git that I just gave up on it and since it is my hobby I don't want to spend much time with git.