Thanks to those giving ideas on my problem discussed in a previous note (sound will not play through Integra speakers when using Prime Video - only plays through TV speakers (all other sound works correctly through speakers).
Also in my note: everything else on TV is great, even up-scaling, with some details in my post.
Response to questions on ARC that I got on this forum after my post:
1) Yes, I contacted Samsung - 2 different tech calls couldn't solve - I registered dissatisfaction & their need to fix
2) Integra/Onkyo no help
3) Sound test did not run properly
4) I tried all other ideas here & found elsewhere but no solution (including power cycling, using different HDMI cables, reconnecting HDMI cables, resets, switching various related options off & back on, etc. on both TV & receiver
Other ideas welcome, thanks.