Using nightly build feed
Add https://www.myget.org/F/avalonia-ci/api/v2 to your package sources:
Update your package using Avalonia feed:
If you experience some problems try to switch NuGet to v2 feed - http://www.nuget.org/api/v2/:
If you still can't update to nightly version try to uninstall Avalonia package and install it again.
Every build (even from PRs and random branches) is getting published to https://nuget.avaloniaui.net/repository/avalonia-all/
To get the version for a particular build you need to check the build number from the build on Azure Pipelines. Then you can use this build to determine PR package version (or just see the logs on Azure).
This feed contains packages with UNTRUSTED source code (basically anyone can create a PR a trigger a build), some make sure to actually read the diff of the corresponding pull request. NuGet packages can contain malicious code even in build-time scripts.