ddns?

Or use addresses like https://192-168-1-1.hp.net (https://192-168-43-123.hp.net, https://10-20-30-40.hp.net, and so on) and a wildcard cert. No harder to document than telling people to go to http://192.168.1.1.

Though they should be more careful than to use to top-level domain as they need to include the private key in the device unless they have the devices call out to have a new certificate generated, perhaps 192-168-1-1.internaldevices.hp.net and so forth.

It would be necessary to use a different private key on each device for it to be secure, so something like 192-168-1-1.internaldevices1489420.hp.net

DNS got fixed to handle dynamic updates in the early 2000's.