Seems like the Ubuntu download is only 22 bytes (empty ZIP file). Is there something wrong?

Yes - the new build will be going out within the next hour with any luck. its been an ongoing issue for a few days and I got a fix for it just moments ago.

you can take a look here for more info

https://capsizegames.itch.io/ai-runner/devlog/511124/towards-stable-cloud-builds

we’ve also been chatting about it in discord and on github as well - feel free to hop into discord if you want to keep up with the latest

The latest build 1.8.19 works again