URL design - Two Yunohost instances, Two local machines

Discuss

I have been troubleshooting DNS recently, and I thought: How would I design my URLs if I had multiple Yunohost instances?
Generally, I’m considering the pros/cons of this URL schema:
{app}.{host}.{location}.tld

What do you think? I’ll give some examples:

example.com → My home. It has multiple machines hosting web servers.

Now, the design of the subdomains is what I’m interested in.

yunohost1.example.com → First instance of Yunohost. This is the only project on machine 1.
yunohost2.example.com → Second instance of Yunohost. This is the only project on machine 2.
nextcloud.yunohost1.example.com → Nextcloud on first instance of Yunohost.
audiobookshelf.yunohost2.example.com → Audiobookshelf on second instance of Yunohost.

The problem – when I attempt to realize this URL structure on a Yunohost instance, I am unable to. When I navigate to “/yunohost/admin/#/domains/add” in the admin UI, it only allows me to create first-level subdomains (yunohost1.example.com), and I am not able to define app-level domains to use for individual apps on that Yunohost instance.

What might be the reason for this? Is there previous discussion I can peruse?