https://steamcommunity.com/groups/SteamClientBeta/discussions/3/2962768084999962...
Been causing issues for people with migraines, epilepsy, vertigo and other conditions since the new library update in late 2019.
Valve has known it's a problem since, at the very latest, a few days after that time.
At the end of may 2020, they started blocking access to the only safe workaround that existed prior to that time.