Hi,
I have not done the modification in lack of of courage - but I thought about it and did some research I'd like to share:
some guy replacing the stepper drivers on an ender board:
->https://www.youtube.com/watch?v=COx7qoW9blE
Original Infos from trinamic:
->https://blog.trinamic.com/2018/04/15/how-to-replace-an-allegro-a4988-with-the-tmc2208/
In the example on the page it looks like some capacitators have to be changed too
some additional general infos on changing to tmc22xx:
-> https://github.com/superjamie/lazyweb/wiki/3D-Printing-TMC22xx-Quick-Guide
good luck