On Linux / GNOME, the Tootle app is quite nice: https://github.com/bleakgrey/tootle. It’s available on Flathub.

Looks like it could use some more contributions with commit access, but it works well as it is!

Edit: But to be fair to the backlog of pull requests, the developer is not located in the most pleasant of countries at the moment, so be patient with them :)

I know that you asked for suggestions on a *mastodon* client specifically...but in case you did not know...technically you can interact with fediverse instances and networks - including, yes, mastodon instances - with other ActivityPub clients too...Just sayin'...in which case feel free to filter for any of a bunch of them here: https://fediverse.party/en/miscellaneous/

No simple C client??

Brutaldon perhaps might interest you? https://brutaldon.org/about

For mobile or desktop? On mobile, Mastodon recently released their official client, and as far as I know it's not web-based.

The problem with the mastodon client made by mastodon is that it is missing a massive amount of features including the federated timeline