With Mastodon it’s less important I think with what local server you choose. You’ll still need to go out and find who to follow. With Lemmy, I think critical mass helps show good content quicker. I’m on hachyderm.io. It’s a solid Masto server. For Lemmy I’m on lemmy.world just because.

It matters even less with mastodon than lemmy, and it really doesn’t matter much here at all

Just yesterday I replied to a post where a similar question was asked, so I hope it’s okay if I just copy-paste my answer:

The best Mastodon instance is the one that aligns with your interests and values the most.

• Are you interested in tech? There’s a couple of tech-focused instances.
• Are you some flavor of LGBTQ+? Some instances do a better job at keeping out bad actors, and you can be around like-minded people.
• Are you interested in gaming? Movies? Art? Writing? Game development? Home improvement? Gardening? Activism? Memes? News?
• Maybe you’re interested in stuff happening in your country or local area?

Why? When you’re looking for new content, and new people to follow, the local and federated timelines of your instance are a good way to do so. Your home timeline includes all the people and hashtags you followed yourself, and their boosts. The local timeline includes all the posts and boosts of everyone on your instance. The federated timeline has all the content that everyone on your instance is following. (Of course you can always follow anyone you like, but I’m making a point about ease of discovering content relevant to you here.)

For this reason, just joining a big, general-purpose is less useful, since you’re just going to get a hodge-podge of random things in these timelines. Perhaps you don’t mind, but I feel like it’s good to point out this feature of the fediverse, as some people might not know, or realize this is a thing.

How? Okay, of course this is silly to recommend without giving you some way to look for these instances. There’s a couple of directories that allow you to search for them. Looking for some briefly came up with https://instances.social/, https://mastodon.help/instances and https://mastodonservers.net/. Also note you can migrate your account from one instance to another, taking your followed content and even followers with you.

I would still go with one that isn’t one of the biggest. My general advice is to find one that fits the vibe you’re going for, communities you’re interested in (e.g. some are focused on art or cybersecurity, etc), or is somehow tied to your locality. It shouldn’t matter that much, though some servers will be a little more (or less) strict with things like federation, content warnings, alt text, etc. Usually the server will have some info telling you some of this, and their admin should be linked and likely has a post or two pinned to their profile explaining some of this as well.

I am partial to kind.social, though have opted to run my own instead of joining up anywhere.

Definitely shop around and find a server that matches the vibe you’re after.

I’d suggest avoiding the largest ones (e.g. mastodon.social) and going for something in the middle.

This server selection wizard might come in handy:

https://instances.social/

The benefit to finding a Mastodon server with a community that you find interesting is that you get a local feed that is somewhat relevant to your interests. If’s far from necessary but it ads one more dimension to surfacing content.

Yes, find a smaller instance, mastodon.social is mid anyways and some servers have them defederated because of spam

smaller instances also usually have interesting local timelines compared to big ones

I usually avoid the top 5 servers

You can choose a server that you find suitable from here

https://mastodonservers.net/servers/top

There are several pages that keep curated instance lists and sort them by category. One of the criteria for inclusion is that the instance must not be too large: e.g. FediGarden and JoinFediverseWiki.

However, you should perhaps consider in advance whether Mastodon is really the right access to the Fediverse for you or rather one of the other services such as Friendica, Calckey, Pleroma, etc. Especially if you are used to a clear structure like on Lemmy, Mastodon can be quite confusing because it is microblogging without context. The instances are connected to each other, no matter what software they are running. The Jointhefediverse.net can help you get started.

Mastodon, and in general, the microblogging side of the Fediverse, is much much more varied than Lemmy or kbin, and your choice of server actually doesn’t matter much because there are so many, and in several different interfaces and flavors. There’s Misskey, Calckey, Pleroma, Akkoma and many others that I honestly consider better than just Mastodon to interface with the Fediverse at large. And, like I said, they all talk to each other just fine. I’m personally using a few Calckey accounts, check out their .org website to find a listing of some open registration instances and go take a look inside!