Samsung Smart One-remote volume control via optical out Home theater system. 

This quick tutorial will show you how to control the volume with an optical out surround system/home theater for all HDMI inputs on your Samsung Smart TV. THIS WILL NOT ALLOW YOU TO TURN THE SURROUND SYSTEM ON/OFF, just volume up & down & mute.
My TV is the UN65MU8000
Current Firmware is: 1250
December 27, 2018
Step#1 Delete all universal remotes on your source Menu.
Step#2 All HDMI inputs should be blank. We start with HDMI #1 and set up your universal remote as a home theater.
Step#3 HDMI-2 will be setup as a Blu-ray player any brand you like.
Step#4 HDMI-3 Will be set up as OTTO/Game console any brand you like.
Step#5 HDMI-4 will be set up as a Set-top box, then “my service provider is not listed” and choose it.
Step#6 So far, only HDMI #1 will change the volume up/down, so from HDMI #1 go to universal remote and select "Use with Home Theater" for each input
Setp#7 Go to TV Input, then universal remote, and set it up as a NEW Home Theater
Step#8 Lastly, change the name of the inputs and it will be changed in main TV menu
After doing this, ALL inputs including apps will be able to work with the Samsung ONEremote volume control.