For many years, DSL/Cable routers by German company AVM, sold under the Fritz!Box brand, did some internal dns tweaking so that when you typed in http://fritz.box it would lead you to the config page of the router in your network. Now, years later, there actually is a .box TLD (Top Level Domain) and AVM forgot to register the fritz.box domain. Someone else did. And activated Certificate Pinning (HSTS). #Oops
UPDATE 2024-01-27: Their dns entries are flaky ATM, sometimes there, mostly not.
A little more background. The box TLD was originally delegated to NS1 Limited, back in October 2016. They sold it to .BOX INC in August 2020. Who in turn sold it to Intercap a few months later, in October 2020. So AVM really had many, many years to find a solution for this problem. Either by registering fritz.box or by changing the firmware of their devices to use, for example, fritz.local or fritzbox.local. Seems it wasn't a priority and this whole thing stayed on the backlog for 7.5 years :)