I have not had to do this with an ARC yet, but with the PlayBar and the BEAM, you go into the sound bar settings to remote set up. It should learn whatever volume commands you have elected to store in the remote, whether the TV volume commands, or some dummy audio commands from a receiver that you are not actually using. The second way will sometimes avoid the TV on screen message every time you adjust the volume.
There is no truth anymore. Only assertions. The internet world has no interest in truth, only vindication for preconceived assumptions.