I think a lot of HN readers would find Foundry VTT to be a good choice - one-off fee, self-hostable, very, very extensible. I think it's worth pointing out tha

I think a lot of HN readers would find Foundry VTT to be a good choice - one-off fee, self-hostable, very, very extensible. I think it's worth pointing out that VTTs (Foundry, Roll20, Fantasy Grounds, etc) don't tend to be good at actual map-making, since the program design and the target users are pretty different, and you're better off with other tools for that. Some of them export into a format that's easily importable into your VTT of choice, complete with walls and such, which helps getting started.