Are Fritz!Boxes available in the US? They're built by AVM (a german brand) and are pretty neat if you want something that's secure, supported for a long time and easy to configure. Add some of their wireless repeaters for coverage via mesh networking and you'll have a guest wifi available everywhere and all is well.
If you select a host in the network overview, there is an option Always assign this network device the same IPv4 address. If you tick that the address never changes. Also in modern Fritz!Boxes port forwarding is associated with a particular host, so I think it also works without the static assignment enabled?
Anyway, I have logged on to my headless GPU machines remotely through port forwarding for years and never had an issue.
In the US when a device is "on the fritz" it is failing intermittently, and the classical solution is to smack it firmly until it works. I suppose a Fritzbox might be perpetually on the fritz.
Same, I have used Fritz!Boxes for years, they are reliable, get updates and are quite configurable. The labs version even has Wireguard support now (they had IPsec before).