Lots of people recommending a proper domain, I would as well (way easier)

Just, if you want to go the complete “independent” route: either make sure all the ylients you plan to use can just accept self-signded certs and skip validation or you need to create your own CA and import those into your clients.

Depending on which clients you plan on using that might be impossible (e.g. for some IoT devices, some Smart TVs and such).

That is why having an proper domain and use LetsEncrypt, ZeroSSL et. al. is way easier.