Dynamic DNS only works if your IP is publicly routable. My ISP (not sure about OP) puts us behind NAT, so the only way to expose services on my network is through a tunnel, like a VPN.
But many ISPs do provide a routable IP. My last ISP did, so it’s not uncommon.
And you don’t necessarily need to own an IP, services like FreeDNS let you use a subdomain from someone else, but a domain can be as little as $1/year (for TLDs like .site and .store), so it’s probably better to just get one. I have like 10 domains, and they only cost $10/year each or so. But if you just want to try out hosting something, using someone else’s isn’t a bad way to go.