The biggest issue might be tire size. 23mm was the norm years ago. Some frames barely allow 25mm and not 28mm. Having 28mm tubeless tires that can be used with pressures in the 60-70 psi range creates a huge ride improvement with low rolling resistance.
A couple of years ago I could find brand new leftover carbon frames for $700-1000. There are few to be found now with all the supply shortages.
If you really want electronic on a budget, sram rival is the answer. With force levers, rim brakes are possible.