Some people talk about mailing lists with a lot of reverence, but I have only ever found them to be extremely ugly and unreadable.
Are there any good clients out there that make them readable? For example a lemmy-like, threaded interface with interactivity? Or for PR/MRs an interface that shows the diffs with syntax highlighting, toggleable unified and side by side diff views, ability to comment within diffs and continue discussions within them (maybe even threaded)?
You could try Mutt or claws mail. Or Emacs, which also still has Usenet support. (In case you don’t know, Usenet is the ancestor of reddit which is the predecessor of the fediverse. Or more succintly, both are Usenet with a web interface, instead of a proper client.)