It can be anything! An apex, subdomain, or even a URL.

Results foradmin.firebase.noctua.test.gotoloop.dev

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2020-04-14T08:20:30.655	2020-04-14T07:20:30	2020-07-13T07:20:30	www.anyhousecafe.com	admin.firebase.noctua.test.gotoloop.dev	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-04-14T08:20:30.307	2020-04-14T07:20:30	2020-07-13T07:20:30	www.anyhousecafe.com	admin.firebase.noctua.test.gotoloop.dev	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-04-14T06:49:10.73	2020-04-14T05:49:10	2020-07-13T05:49:10	admin.firebase.noctua.test.gotoloop.dev	admin.firebase.noctua.test.gotoloop.dev	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-04-14T06:49:10.522	2020-04-14T05:49:10	2020-07-13T05:49:10	admin.firebase.noctua.test.gotoloop.dev	admin.firebase.noctua.test.gotoloop.dev	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3