how can I install it with a subdomain?

[Jorgelig]

I want to test it on a linux VPS server, how can I install it with a subdomain?

[thrownullexception]

All you need is to run npx hadmean and set up Nginx as a reverse proxy to the port on the desired subdomain. Et Voila!
https://bobcares.com/blog/add-subdomain-nginx-digitalocean/ is a good post on this.

Other than the above direction, if you need more guidance, I suggest you talk to someone with some DevOps experience