You can build an end simple end user system with DDNS and OpnenVPN on the home router without going with static IP or cloud based services (outside DDNS obviously)
Having done this, I can tell you many smart home users do not even know how to change the password on their WiFi router. Installing OpenVPN is a non-starter.
What if someone packaged openvpn on a $50 box with home assistant pre intalled and had gui wizards to set everything up? Seems pretty doable to me. Just needs a founder.
