Our bikes have 10-11speed compatible wheels, however SRAM and Shimano have extended leadtimes due to COVID-19 supply chain issues, so we have built bikes that can access the eBay and back of the shed market.
When derailleurs become more available this is where we will stock them.

Our bikes are designed for derailleurs that all operate with cables, however you can still use electronic.

Cheap derailers, work 98 to 100 percent as well as the expensive ones.
Shimano doesn't want you to start off on a cheap bike, not knowing how to shift, and hate its cheap derailer, so they make sure they work as well as their expensive ones. XT & XTR have both had some serious engineering to make them lighter.
We would recommend a mid-range derailleur like Deore or SRAMS equivilant.

There are other options, like manual changing using a chain tensioner, or going dingle-speed and using 2 chainlines.
The Crane Brothers did this in the 1980s crossing the Gobi Desert