Most people are probably moving to GH actions. You can simply copy someone’s workflow file into your repo and you’ll be up an running. Here’s an example
The actions minutes per month are free for public repositories, according to https://github.com/pricing, and I believe that holds for organizations too but am not sure.
GitHub was acquired by Microsoft in 2018. Is this question about how bad it is that your CI will be dependent on Microsoft?
Currently Cairo CI runs 6 jobs on Travis out of the 5 concurrent jobs available for the whole organisation, so I’m not sure what’s your concern with using 14 concurrent jobs out of the 20 available on GitHub Actions. GitHub Actions also uses beefier machines, so jobs tend to be slightly faster than on Travis