Classic Amazon "Prime is our mismanaged dumpster fire" behavior - slowly roll out a new feature over weeks/months, dont provide the necessary access/controls for it, dont inform/train your own support teams about either the features/controls, and let whatever happens happen.
Well, at least Prime's subtitle backgrounds on Roku are now working properly....oh..wait..no...still cant figure it out...many years in...
BTW, what is the Prime app version for either of you? @autoplaysux @MPStreamer (highlight the app, press Options (*)..)
On FireTV devices, this can be disabled in Settings/Preferences/Featured Content/Allow Video Autoplay for the FireTV player, though the Prime app only allows you to mute them (Settings/Previews/Mute Previews).
This would be the obvious place for a global setting: https://www.amazon.com/gp/video/settings/playback/ref=atv_set_playback However, it doesnt exist.
Considering it took them 5 years to follows NetFlix's forced autoplay preview lead, and considering it took NF 4 years to finally allow users the ability to disable it, users can expect Prime to add such functionality in 2025.