Mercurial (hg) is a fine alternative that was widely adopted in the early 2010s, but has gradually lost mind share to git. Actually every company that I worked for in the 2010s had a Mercurial service (maybe unloved). I think companies adopted it because command line hg is closer to svn, and more obvious in general, so it was an easier migration from svn. I also think out-of-the-box hgserve is easier to understand than git serve, so before tools like GitLab and Gitea it was easier to host on-prem.

Mercurial’s data model is indistinguishable from git, and IIRC it even slightly pre-dates git. The main thing git had going for it was GitHub, but that was enough to build a positive feedback loop and come to dominate the mindshare.