Fedi.Tips@FediTips@social.growyourown.services
p.p.s. The server mastodon.social is NOT a good place to sign up, for many different reasons (more info here: https://fedi.tips/its-a-really-bad-idea-to-join-a-big-server).
If you just want one alternative, https://mas.to is a much better option. It's reliable and has been online since 2019, and doesn't suffer from the problems of mastodon.social.
If you want to choose from a wide selection of servers, there are human curated lists of well-run reliable servers at https://fedi.garden and https://joinmastodon.org/servers
Novem@NovemDecimal@im-in.space
@FediTips@social.growyourown.services
If I recall correctly, the official mobile Mastodon app have users sign up on the default instance which is... as you guessed it, mastodon.social
This, doesn't help either because a lot of newcomers are most likely mobile users.
I know that this is to make it easier for newcomers, but I think it just buries the onboarding problem rather than solve it.