I had SalesForce docs also saying they accept localhost:8100, but could not get it to work, then reading deeper I saw they were specifically talking about https://localhost, which to be honest I did not even know existed, after trying to add https to localhost unsuccessfully I just went the docker route.
Just helped cut out one possible cause of problems.
@wappler_ambassadors, anyone know how to get localhost with SSL https://localhost just out of interest.
Moved this last part to a new thread, because I did not want to hijack this one.