Looks really interesting! Does the self-hosted version support OAuth or other authentication methods to manage users through an external identity provider?
My typical response from GitHub Enterprise support has been fantastic over the years. I'll also note that after GitHub Actions/Packages came out on Github.com the lead time for support response did increase substantially for non critical tickets due the increased support burden for those new services. My most recent tickets have been answered promptly so they must have figured out the staffing issues.
You should be well aware that actual architecture of GitHub Enterprise isn't truly highly available (1 active and 1 or more standby instances) unless you are a huge customer to support clustering mode. Which means you likely need to take downtime to implement upgrades since they typically require rebooting the VM.