I would disagree that Radiant is no-frills. There’s plenty of great features, they just aren’t forced in your face in the default UI.

I’m just a crazy app tester that tries just about every one that comes out. 😅

Here’s some of the more unique ones.

Multi Tags (create a filtered timeline based on up to four hashtags with and, or, not conditions)

Timeline Filters applied to any timeline - home, local, federated, lists, hashtag, multi tag. Filters can be applied for media, links, posts only, boosts only, post and replies only.

Threaded posting from the post compose button.

Translation of posts isn’t unique but it’s done very well.

client for decentralized social network Mastodon which focuses on simple and functional design

For those who are looking for something similar available on both Android and iOS: Recommendation for tooot. Special feature, especially for users of small instances: It loads the comments from the original instance when you open toots, so you don’t just see comments from users who are known on your instance. I haven’t seen this on another app yet on Android.