I used https://tweetdelete.net/ a few years back. I had to pay for a premium account for a month to do it but it was only a few bucks. I’m not sure what “expensive” would be in your books.

I don’t have any input on your hardware but for software you could look into Ente. They have a self-hosted version.

You can’t send out emails using Apple’s temporary email service whereas you can with Proton’s.

Ah, fair enough. Sorry, I don’t have any invites.

Pretty sure it’s free registration.