Error "Could not parse framework 'net6.0'. Try to update or install again or report a paket bug."

Description

Trying to upgrade a project from net5.0 to net6.0 I got the error message from paket "Could not parse framework 'net6.0'. Try to update or install again or report a paket bug.". I just upgraded to last version (stable and preview) to no avail: 6.2.1 and 7.0.0-alpha003.

Repro steps

1. Clone FSharpLint master.
2. Upgrade FCS to latest version.
3. (Because the previous upgrade doesn't work in .net5.0: ) upgrade all projects and CI to .net6.0.
4. Build fails, so I upgrade paket to 6.2.1.
5. Build still fails, so I upgrade paket to 7.0.0-alpha003.

Expected behavior

Should build?

Actual behavior

Throws error:

Run dotnet fake build -t Test
Extracted Paket.Restore.targets to: /home/runner/work/FSharpLint/FSharpLint/.paket/Paket.Restore.targets (Can be disabled with PAKET_SKIP_RESTORE_TARGETS=true)
Performance:
 - Cli parsing: 283 milliseconds
 - Packages: 114 milliseconds
 - Script analyzing: 206 milliseconds
 - Runtime: 686 milliseconds
There was a problem while setting up the environment:
-> Error in paket.dependencies line 3
     Could not parse framework 'net6.0'. Try to update or install again or report a paket bug.
Hint: If you just upgraded the fake-runner you can try to remove the .fake directory and try again.

Known workarounds

Nope.

Each of the steps described above is a commit in the following experimental branch (where you can see the CI log): https://github.com/knocte/FSharpLint/commits/fcsAndNet6upgrade

Start with line 3 of paket.dependencies and reproduce the failure using dotnet fake build -t Test. Review the CI logs and commits on the linked fcsAndNet6upgrade branch to determine why net6.0 is rejected; done means the project builds without the framework parsing error.