I had the exact same problem with Render, but I wouldn't expect them to handle this situation because I'm guessing it's kind of an edge case? I ended up using a DigitalOcean Droplet + CapRover to do this, and then wrote a giant article detailing all my steps in case that's useful: https://alldjango.com/articles/serve-multiple-django-sites-f....
I don't think that's an edge case. I'm addicted to creating new side projects and I think there's more of 'us'. These projects usually don't get any traction but I like that they work, they are there, accessible globally.
I'm hosting a few using portainer and cloudflared on Synology NAS. This way everything is free, I have unlimited HDD and 10GB RAM. I keep running into some small issues and the CPU is terrible, but it works. :) Most of the time... Which is enough for me.
