Error while using Jet Brains Rider IDE

I get this error on the “Toolset, Environment” tab when opening Jet Brains Rider IDE for external script editor:

Generator ‘MonoScriptInfoGenerator’ failed to generate sources

Only allowed to have one file passed in with extension ‘.AdditionalFile.txt’

It doesn’t matter whether the project is fresh or not and I don’t know what couses it to appear.

Same problem. JetBrains says this is a Unity problem. Found this as a solution, but am unable to judge possible repercussions: