Gridsync's GitHub-integrated CI is presently spread across multiple providers -- each of which comes with varying degrees of reliability, responsiveness/speed, and maintenance overhead but none of which alone satisfies the highly-desirable requirement of being able to run tests on all currently-supported platforms in a streamlined fashion. To ease future development and configuration maintenance, it would be preferable if the project's CI system could become more unified such that a push or PR could run tests reliably across all supported platforms and report test results in a single location.

Of the currently available options, GitHub Actions seems like the strongest contender for improvement in this regard: its strong integration with GitHub itself should ensure more immediate and accessible test/run results on pushes/PRs, while its support for various operating systems "out of the box" (specifically, various Ubuntu releases, macOS, and Windows -- with additional support for self-hosted runners) allows for testing on supported all platforms via a single configuration file.

The Gridsync project should consider switching to GitHub Actions and, if all goes well, discontinue using Travis-CI and AppVeyor.

(In the future, it may also be feasible to also replace the current fleet of Buildbot-workers with self-hosted GitHub Actions runners for the purposes of further improving or streamlining the release process (such that, e.g., a pushed tag could generate signed/notarized builds, prepare a changelog, upload to GitHub Releases, etc.) but such improvements should be considered out-of-scope for this Issue.)