Dumpster Diving
I have a number of Logitech culled mice from the disposal route*, with UNR's (I know right & re-paired as needed via the software) & also picked up 3 K850's from a Govt disposal location. Really handy as those KB's will sync to one of three paired UNR's.
So this isn't likely to impact me for some time, but it really is a right PITA, that in the event I might have to buy new kit to have something that's not going to work with the rest of my salvaged stuff.
*Actually kinda pissed that I let a M215 & UNR slip through my fingers for $1 in a thrift store the other week.