Canon EX flashes have contacts for communicating with camera. Those communication works only with Canon cameras. So, if you want to use EX flash on other than Canon camera you must do next: You must isolate all contacts on flash except central contact. You can then try to use commands on flash itself to adjust zoom of flash head, how strong flash will fire and
everything else. So, you will have manual flash not automated flash, that means you will not have TTL mettering, you will have to thing about aperture of lens, subject distance, subject/scene brightness and everything else one should think of when use manual flash.
That way you can use Canon EX (or any other flash which have manual commands on flash itself) with any camera.
Only problem is using electronic cameras with old flashes which have high trigger voltage (up to several hundreds of Volts), those flashes can destroy electronic circutcy in camera. Canon EX flashes have max 6 Volts of trigger voltage, so no problem with EX flashes. And newew flashes also have international standard voltage (12 or 24 Volts max, I am not sure), so no problems with new(er) flashes too.