I play on 1.21.1 and it is not clear what versions work with 1.21.1 if any I'd reccomend you label them to the versions they work with.

For me that's a pretty clear description.

There is no release for 1.21.1 so you either have to build from the 1.21.1 branch yourself or, while it's less than 90 days old, download the Artifacts of the latest CI run on the 1.21.1 branch. (List of all successful CI builds on the 1.21.1 branch is here, select the topmost entry, download and unzip "Artifacts" at the bottom, you must be signed in)