Sandbox servers

A while back I heard some advice about using a sandbox server (rather than the official server) to test out bot code.
Are there servers running out there that I could use, or would I have to set up my own?

https://wiki.musicbrainz.org/Development/Sandbox
seems to be woefully out of date.

Sadly I’m not sure if there’s any sandbox servers running at the moment.

@Bitmap, do you have one available by any chance?