Some Broadcasters require a Harding Test which is patented and proprietary, it creates a Certificate; thus getting someone to accept liability isn't going to be free.
You can find a number of places online that will test a video file (or Game, Poster, Art, etc.) but those aren't free, the Harding website has authenticated tests and support.
Free software claiming to perform the same checks (so when you submit your work, it won't be rejected) is available from the University of Maryland in the form of PEAT, their Photosensitive Epilepsy Analysis Tool.
Note: Restrictions on use
The Photosensitive Epilepsy Analysis Tool (PEAT) was developed to provide a free resource for Web designers and computer software developers. Use of PEAT to assess material commercially produced for television broadcast, film, home entertainment, or gaming industries is prohibited. For broadcast, film, home entertainment, and gaming applications, the Harding FPA software should be employed.
To get the real thing, a Certificate, you'll need to pay. To get software that claims to do the same thing without accepting liability or providing the authentic Certificate is possible, I found that source with less than 10 min. of searching.