For companies with resources for infrastructure, sure.
For OSS, the unlimited free minutes of multiplatform CI offered by GitHub are literally impossible to replace. Maintaining runners yourself to do the same things would be somewhere between a part- and full-time job.
> For OSS, the unlimited free minutes of multiplatform CI offered by GitHub are literally impossible to replace.
Yeah, how you think the ecosystem got by before GitHub even had actions? Y'all don't remember Travis CI et al anymore?
There are more CI services than what Microsoft offers the world, sometimes it's worth looking around a bit.
> https://docs.codeberg.org/ci/
"Codeberg is a non-profit, community-led effort that provides services to free and open-source projects, such as Git hosting (using Forgejo), Pages, CI/CD and a Weblate instance."
Never say impossible.
Github is still "new" to a lot of us. OSS existed well before it, and will continue to exist well after.
If Codeberg starts offering Mac and Windows runners alongside their Linux ones for free (or at an achievable price point) for a modest OSS project I'll certainly look at it very closely. If all I needed was a Linux runner, I'd probably be on there already.
And yes, if we make OSS just about hosting the code, things are much simpler. If you're a piece of desktop software though, and you have users, they'll typically (and reasonably) want auditable signed binaries on all the platforms you support, which requires multiplatform CI.