We just invested a lot migrating 300+ pipelines from Azure DevOps to GitHub Actions. What a bummer timing-wise. Anyone got an alternative to GitHub Actions?

You can run your own github actions compatible-ish server. https://github.com/nektos/act

Personally my favorite is probably drone-ci.

I'd suggest not buying in too hard on any one of these CI systems and just writing shell scripts. Shell scripts are portable, and you can use whatever to trigger them.

Forgejo has open source reimplementation of github actions

Fogejo is self-hosted Github with actions.