The company I'm currently at uses a self hosted instance, which due to our "security"* constraints we're grossly behind in updates. Not to say that's Gitlabs fault at all, but the amount of issues we have near daily is hilarious (if it didn't simultanously crush productivity).
That said, I recall issues with the Gitlab Enterprise Support / whoever we contact about our license etc, mostly to do with slow or poor communication. Requests would sit for a month before we got a reply, often dismissive or generally unhelpful, though we _were_ on an outdated version so I don't blame them.
I vaguely recall an email about support ending on self hosted instances? I can't recall the details, but I know it triggered an internal investigation into moving away from Gitlab. EDIT: Pretty sure I'm remembering self hosted Jira, a quick Google search shows Jira EOL but no Gitlab.
All of that said, I largely blame my company for the failures here. I wouldn't expect any company to support self hosted, outdated versions. The support issues were annoying, but I'm also not sure how much I can blame Gitlab for that. I'm also struggling to remember the details, so take this as one mans hazy annecdote.
* film industry, security by obscurity in the worst ways, leads to incredibly outdated and neglected tech (we only _just_ transitioned to Python3, and that's only the core services)