Bolt causes built to fail (Windows standalone, Unity 2021.1.0f1)

I tried to build my project after add Bolt plugin, the build failed with this error:

What am I missing and how to fix that?

Thank you!

Can you submit a bug report for this issue? This looks like a bug on the Unity side.

I had the same problem… My issue was solved by changing the API Compatibility Level to .Net Standard 2.0 from .Net 4.x in the Player Settings->Other Settings.