This doesn’t really apply if you’re port forwarding to a specific device. In that case you know that you have told your firewall to forward port 80 & 443 (for example) to your web server and you know what ports that has open. I would not be using UPNP on the other hand as that seems dangerous especially in the IOT era.
Keep in mind you can always use a different DNS provider who does support dynamic dns. For example you could use cloudflare (free) with a domain bought from Pork Bun.
The article makes it sound they cost over $1,000 (USD?) and were impossible to find but here in Australia I never had any issues finding and unless you were going for the extreme versions, there closer to $5-600AUD which made them a great fit. All we can hope is that there’s a few other brands who are willing to fill the space with equal quality products.