I am a brand new user of Affinity Photo. I was following the guide at Get Started for selecting a channel from the Channels Panel, but control-click was not bringing up the contextual menu for the channel. It seemed that I had no way to work with channels.
I discovered, however, that I could get it to work if I control-clicked in the narrow border *around* the label for the channel. The attached screenshot shows the contextual menu that I got when the tip of the arrow was about half-a-character below the "u" in the word "Blue". Clicking on the "u" itself failed to bring up the menu, so using repeated trial-and-error I could map out a long rectangle where responsiveness to the control-click was being occluded. This behavior occurred with every channel (Composite, Background, Pixel Selection), and persists with the v1.9.1.219 beta.
Curiously, the occlusion seems to affect only control-click, because I can still alter the state of the channels by an ordinary click, e.g., clicking on the label "Composite Red" enables Visible and Editable for that channel alone.
My computer is a MacBook Pro with the built-in trackpad and macOS 10.15.7.
