[lima]

Reviewable is another similar review improvement tool for GitHub: https://reviewable.io

...or just use Gerrit[1], which can do everything these do out of the box, and has a much nicer workflow than GitHub once you got over the learning curve.

[1]: https://www.gerritcodereview.com

[Macha]

I've never actually used Gerrit personally, but I've twice been on teams that had recently dropped Gerrit at the time I joined (once for Bitbucket/Stash, once for Github Enterprise), and neither seemed to ever look back.