DistroTest
DistroTest (Test it before you hate it...) was a website where you could run any Linux distro you wanted. VMs ran on QEMU on Debian. The site was last online August 6th, 2022. The VMs on DistroTest did not have internet access because users were attempting "forbidden" things (as stated on the website). Before the shutdown date, you could buy the domain.
Shutdown
On August 8th, 2022, distrotest.net became parked and up for sale. The site stayed like this until August 20th, where it was purchased by an anonymous user and turned into a Wordpress blog. The blog does not have any relations to the original site and the owner of the site continues to make posts about random, obscure products. Some are slightly NSFW.
The other domains remain parked as of September 5th, 2022. The original owner has not posted any updates on whether the website will return. The servers running the website are presumed to still exist, as the website did not state the servers will be shutting down, just the website.
The site seems to have over 16,000 posts since August 20th, which means there is probably a bot running making all of these posts.
Alternatives
While it is pretty garbage, Onworks is similar to DistroTest, However it does run outdated versions of certain distributions, so if you want the newest stuff, you're out of luck.
Around May 2023, DistroSea was launched, inspired mostly by this website but with a medium-sized catalog of Linux distributions.