The easiest way to tell is to download the manual for a camera you are interested in and look for the "System Map"
For the R5:
Yes they will work but the AF Assist Beam Emission method is different. Mirrorless cameras can't detect the "Infrared" AF Assist Beam. This beam is just visible red light with a grid pattern designed for DSLR AF sensors. The speedlite will use Intermittent Flash Firing (Disco Flash) for AF Assist. But depending on the ambient lighting an LED AF Assist Beam may be projected by the camera instead of the speedlite.
