We considered switching to Git as well for a similar reason (GitLab). However we discovered Phabricator provides similar toolset at GitLab and also supports Mercurial. It's open source - you can run a local instance (no cost but also no support) or pay for them to host. They also recently started a free plan where they will host an instance with up to 5 users.

https://www.phacility.com/phabricator/

We've been using it for 2+ years at this point and glad we stuck with Mercurial.