I believe focus bracketing forces use of electronic shutter, and so far among Canon mirrorless bodies only the R3 can use flash at all with electronic shutter.
The R3 does support focus bracketing using flash. It waits for a Canon flash in the hotshoe to be fully charged before taking the next frame, but also lets you set an interval delay to allow for a 3rd party flash (including via a PC sync cord) or wirelessly-controlled Canon flashes to recycle.
https://cam.start.canon/en/C010/manu...ng-1_0280.html