Setup paying hot wallet btcpayserver to joinmarket all on one machine, on regtest:
Follow installation instructions from scratch as per: https://docs.btcpayserver.org/LocalDevelopment/ (note, there is another setup description, but it is specifically for coding and debugging, using visual studio, here: https://docs.btcpayserver.org/Contribute/ContributeDev/ContributeDevCode/#visual-studio-setup)
docker-compose up devcommand specified there, run
dotnet run --launch-profile Bitcoinfrom BTCPayServer directory (should not need to change any config)
Load http://127.0.0.1:14142 to get the BTCPayServer UI
Create an Admin account (check the option) with a random email and password. New screen should show 'Regtest' and 'Server Settings'.