Seems like Android builds have been offline for two months.
Builds are now fixed - the docker plugin had broken for some reason.
Thanks for alerting me.
Would it make sense to drop the Jenkins build machines and just use the Travis and Appveoyr builds to produce the downloadable artifacts? That could relieve a bit of your budget for the builds, plus the builds would be really official (and it would free my home computers

If it's possible that would be a good idea. We would probably want to host the artifacts ourselves but if they can be generated in the same way as our CI it does make sense.
Android and FreeBSD builds seem to be broken. MacOS builds have been down for a while, but there's probably not much that can be done, unless someone has an Apple-device or looks into cross-compiling.