I agree, my current daily driver is a Keychron and so far I haven’t had a problem with the Bluetooth when I use it. I use it wired most of the time but a 2.5Ghz dongle would be fantastic.
I just saw the Royal Kludge RK918 today and it looks just like the out of production Anker keyboard I have. It is solidly built and looks great. The only drawback I see is it appears to be like the Anker in that it is a hardwired cable, no customizing with aviator cable or such. Not all RK keyboard are like this and many have the dongle like yours.
The old keyboard looks just like my first entry into this space only it doesn’t have the Aukey badge. My keyboard is an Aukey KMG12 keyboard (full size aluminium plate base, blue outemu switches) with Matrix Keyboards Hulk Smash keycaps.