What hotshoe flashes are compatible with my Canon EF film camera?

The Canon EF film camera did have a dedicated flash called the Speedlite 133D but it was very low powered and difficult to use. It was called "The CAT System" (Canon Auto Tuning) and needed a ring installed on the front of the lens in order to transmit focus distance information to the flash.

Instead, I would recommend any film era Thyristor flash from the late 1970s and early 1980s. Get one with a bounce head for more natural looking light.

Two Canon examples would be the Canon 199A and the 299T. They would both work very nicely with your Canon EF film camera.

A more modern option would be the Canon 580EX II or 600EX RT. These modern Speedlites are fully compatible with modern digital ETTL flash, but both also have an option to use “External Auto” mode that uses the old Thyristor system of the film era.

With any of these Thyristor flashes, you just set the camera aperture and ISO to match what is set on the flash, and the flash uses the external light meter at the front of the flash to automatically adjust the light output for proper exposure.

Any single pin flash will work. Do not use a modern unit. It is a waste of $. If you want period relevant equipment, Vivitar made excellent basic strobes back in the day. I've also had good luck with Starblitz/Hanimex strobes. Units with tilt/swivel heads and twin strobes are the most useful, in my opinion.