Sign-up with https://www.appveyor.com ?
At least running an part of the tests would maybe help with windows regressions like:
https://github.com/matomo-org/matomo/issues/11731
https://github.com/matomo-org/matomo/issues/12290
But as far as I know only one job (not build) at the same time is free, so maybe only run on commits to 3.x-dev.