I am deliberately not promoting flagship instances on fedi.garden (there's a maximum size limit after which instances are delisted).
But it seems like GTS currently doesn't have any public instances at all? GTS instances are all ones where you have to already know the person who runs it? If someone doesn't know anyone who self-hosts, they're sort of shut out of using GTS?
(Again, not a criticism, but this is why GTS is difficult to promote to new non-tech people.)