plenty of them. it's been around since 2016 and has about 1.8 million active users.
Discussion
member.cash or mastodon one o them?
can you cross an account to nostr account to fediverse?
not familiar with member.cash. the top servers are these. https://void.cat/d/9PukEcFTVMVVaqsKaKecF1.webp
it's hard to recommend a specific server, but what people usually do is sign up for something like mastodon.social, mastodon.online or mstdn.social and then later they find a permanent home elsewhere. i have a server at berserker.town myself.