Hi Chris, welcome to the forum!
I can confirm I’m able to switch from NET input channel (listening to music played from NAS) to ARC input channel by using the remote:
- First I have to press on the “PC USB” button on the Arcam remote, Arcam console states ARC input channel is selected but no TV sound is played yet.
- Next I have to select tools button → receiver option on the Samsung TV remote in order to play TV sound through SA30.
I guess the second step is required to forward the TV audio from TV speaker to the receiver and is required on a Samsung TV only. Different TV brands might handle this differently.
In a previous SA30 firmware build discussion (this article has been unlisted) it was partly possible to switch to ARC input channel (remember @Mark’s pun: Icing on the ARCake 
).