That's not true, one can have IP addresses in certificates, it's just very rare because virtual hosting makes "single IP" services rare nowadays: https://www.rfc-editor.org/rfc/rfc5280#section-4.2.1.6 ("Defined options include an Internet electronic mail address, a DNS name, an IP address, and a Uniform Resource Identifier (URI).") OpenSSL uses "IP:" syntax in their subjectAltName field (e.g. https://mta.openssl.org/pipermail/openssl-users/2016-Septemb... ) and the CAB seems to be on-board, subject to some "well, watch out for ..." language https://cabforum.org/working-groups/server/guidance-ip-addre...
It's probably not worth it anyway, because you're now stuck with that single IP, for little benefit. In general IPs just don't get HTTPS certificates acquired for them.
https://help.zerossl.com/hc/en-us/articles/360060119973-Is-I...
Real-world counter example of an IP address available over https:
This is not so great for radio streaming as a lot of them still use http shoutcast servers (often with direct ip instead of domain name, so no https there anyway).