I would like to host a second forum on an OVH VPS. Main standalone discourse instance runs on the domain root (https://zbeul.org) and I want the new one to be ran on https://mao.zbeul.org.
I figured the best solution would be 2 standalone instances with nginx proxy_pass in front.
Your plan should work. Or both instances on non standard ports. I recommend using caddyserver as the front door. That’ll give you https in both sites with no extra configuration.
Also, if you want to save some resources, you can use this, it’s just a bit more work than 2 standalones, but uses half the resources: Multisite configuration with Docker