On Sourcehut, Mercurial is a first-class citizen. The open-source implementation is community maintained, so as long as Mercurial's community remains, Mercurial support on Sourcehut shall endure. Join us!
This script will migrate your Bitbucket repos to Sourcehut. Just run the script and follow the prompts.
Note: to limit dependencies, this is just a shell script, and as such it's kind of hacky. Your mileage may vary. One thing which is known to cause problems for some users is Bitbucket repos whose descriptions have newlines in them.