Try going to the home page of instances of accounts you like (or of instances that seem interesting) and browsing their federated feed (tap globe for “live feed” then hit “all”), you can discover tons that way.

As a general mastodon instance mas.to looks good and is a nice size with a good stable history.

https://mas.to/about

You can find established, more established instances on the fediverse by surfing around a bit fedidb

https://fedidb.org/