The reason I favor GitLab over GitHub is that I can install it on a dedicated server and have blazing fast performance, which helps development performance on an every day basis.
I've been maintaining a bunch of deployments of all sorts (k8s, docker-compose, baremetal) for the last years for several customers of all sorts of size, the upgrade process has always been pretty smooth, sometimes I ran in edgecases yes but always found a solution.
My deployments are always up and kicking, unless I'm messing with the configuration and doing some mistakes.
I highly recommend hosting your own GitLab instance, even on a single server.