Setting up custom GitLab runners can be cumbersome in the beginning! We faced that multiple times with various customer projects for which we were using GitLab.com managed repos. That's why my colleague and I recently built a "GitLab Runners as a Service" [0] -- simply use your self-managed GitLab or GitLab.com account to login, adding pipeline runners is a 1-click operation! Under the hood we provision a Hetzner machine for you runners and automatically connect your GitLab group or project to it. Happy to hear your feedback!
[0] https://rocketrunner.io/