I haven't really seen anything else quite like it (though it does have a long way to go still).
People try to roll their own from-scratch solutions or plug in an off the shelf tool here or there and their idea-to-production pipelines are generally worse or incomplete in comparison. Most of the architects of these things only care about their corner of the solution space and the rest are either neglected or have their own champions and their own siloed solutions.
Nothing off the shelf quite resembles it either. If you e.g. buy and use the entire Atlassian suite and train and get everyone to agree on the desired flows and practices, so much is left to you to design that no two such systems are likely to be similar, nor (in my experience) is any one such system likely to be very effective or efficient in daily use.
I'd really enjoy seeing Gitlab mature and expand, I would love to work at an org that adjusted itself to fit something like what Gitlab is trying to be, instead of trying to make their hodgepodge of tools adhere to their personal tastes and political dynamics, etc. (a Sisyphean task as those landscapes are under constant arbitrary change).
They can do this by using the best / most fitting open source software for each task and integrating it, also by focusing mostly on kubernetes while still providing enough flexibility for other options. You just don't get to use the whole feature set if you're not on kubernetes.