Note: From 210405, Turnkey core and MDrivenServer core allow for HTTP access by sending a parameter—no HTTPS—as described here: LocalServers

To let the server talk over SSL without security warnings, SSL certificates for localhost:PortNo must exist. This is what is typically called a Developer Certificate.

To register the developer-SSL cert, you must have the .netCore SDK installed.

If you already have it, jump to step 2:

1. Download the .netCore3.1 SDK https://dotnet.microsoft.com/download/dotnet-core/thank-you/sdk-3.1.404-windows-x64-installer and install it.
2. In a cmd window, paste this and press Enter:

dotnet dev-certs https --trust

If you suspect that there is something wrong, try to clean it first:

dotnet dev-certs https --clean
dotnet dev-certs https --trust