What Speedlite is really compatible with R5, Mark iI camera- I am not finding any consistent info

[March411]

I use the Westcott FJ80 II M Universal, primarily in manual for macro but have shot in TTL and HSS with success. You do have to update the firmware to the latest version to get the full functionality.

[kvbarkley]

It has the traditional 5 pin contacts as well as the new multi pin connection, so it can work with pretty much any Canon flash, but I would recommend the EL-5 or EL-1

[deebatman316]

Some speedlites require the AD-E1 hot shoe adapter to maintain a weather sealed connection. The EL-1, EL-1 Version 2, 600EX II-RT, 600EX-RT, 600EX & 580EX II are the only speedlites that need it to maintain weather sealing. Other EX series DO NOT require the adapter because they don’t have the weather sealing gasket. The EL-100 doesn’t need it either it uses the legacy 5 pins as older EX series. The EL-5 & EL-10 use the new multifunction hot shoe. 3rd Party speedlite compatability is up to the 3rd Party Manufacturer NOT Canon.