https://about.gitlab.com/solutions/open-source/join/
They offer everything in Ultimate, including 50k hosted CI minutes, and the requirements seems reasonable (basically, everything needs to be public, have an open-source license, and you can't profit from add-ons or services).
The drawback is that it looks like you have to apply for it to use it.
Next to using GitLab.com SaaS, Open Source Program members can also choose to self-manage their GitLab instance -- like Arch Linux.
> The drawback is that it looks like you have to apply for it to use it.
This is a requirement, yes, but should not take too much of your time. You can learn how the process works in https://handbook.gitlab.com/handbook/marketing/developer-rel...
update: ahh I see there is a "migration" popup on the 404 page.
[1] https://about.gitlab.com/solutions/open-source/join/
[2] https://handbook.gitlab.com/handbook/marketing/developer-rel...
If you have a commercial offering, you can probably afford to pay for your tools.