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

Results forrun.themer.app

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2020-03-15T17:24:08.292	2020-03-15T16:24:08	2020-06-13T16:24:08	zinglio.com	run.themer.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-03-15T17:24:08.128	2020-03-15T16:24:08	2020-06-13T16:24:08	zinglio.com	run.themer.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-01-15T16:57:54.669	2020-01-15T15:57:54	2020-04-14T15:57:54	horuscross.turnosweb.app	run.themer.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-01-15T16:57:54.406	2020-01-15T15:57:54	2020-04-14T15:57:54	horuscross.turnosweb.app	run.themer.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-01-15T14:08:23.367	2020-01-15T13:08:23	2020-04-14T13:08:23	run.themer.app	run.themer.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-01-15T14:08:23.143	2020-01-15T13:08:23	2020-04-14T13:08:23	run.themer.app	run.themer.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3