Hi NonsensicalCentipede91 ,
Currently, the UI looks for the apiserver in a fixed port on the same host, or, if using subdomains (and not ports), in a fixed subdomain (app.)

Would it be possible to add some domains that are more train-specific. e.g. (trains., trains-file. and trains-api.*)?

Yes, when you access from app. it uses file. and api.*

Did you use the templates from the Trains Server K8s repo ( https://github.com/allegroai/trains-server-k8s )?

We host our projects on cloudflare and they don't allow sub-sub-domains. Therefore we would need a new domain for trains if we don't want to let api.* be taken.

As far as I remember, the UI can support the mode used there as well

Well, you can always use your own proxy or load balancer. We'll probably add some way of configuring it in the next version 🙂