Not an issue but a standard warning. Fediverse instances don't auto-populate, and the author of the original project¹ must have thought it was a good idea to raise awares of that by putting this warning.
But if it bothers you and you use Ublock Origin, though no native option to dismiss it are availabe, you can put this in a new line of Ublock Origin's custom filters tab:
thebrainbin.org##.alert__info.alert
¹Mbin's a fork, and the original software's no longer worked on