This setting is missing from Accessibility.

https://support.zoom.com/hc/en/article?id=zm_kb&sysparm_article=KB0058139

Sign in to the Zoom desktop client.
Click your profile picture, then click Settings.
Click Accessibility .
Select the check box to enable Automatically dim video when flashing images or visual patterns (such as stripes) are detected.

This is not listed under accessibility.