using brave from snap 1.60.118, running Ubuntu 23.10, I ran into that problem:
I was browsing a local application under http://localhost:3000/, working well. Due to some misconfiguration/configuration test, the application was set to set a Strict-Transport-Security header, although never offering TLS. Since then, brave insists on using TLS, even on the URL http://localhost:3000/, refuses to talk plaintext HTTP, thus cannot connect to the application anymore.
I did not find any setting in the settings, to reset or cancel this.
Not even deleting the files in ~/snap/brave/current/ actually helped.
So the question is:
How would one cancel Strict-Transport-Security settings for a particular URL/site?