A lot of effort is put into keeping Files Gallery nice and clean also for viewing, and this means keeping distracting elements from cluttering the interface. For desktops (with mouse), it is very easy to access the context menu without having to have the three dots visible at all time.
robertwilkin An iPad has no hover function and the suggested alternative of tap-and-hold mostly doesn't work as there is initially nothing visible to tap
It's not quite clear to me if you have tried this from the iPad. Although iPad does not have "hover" like you know it from using a mouse, "hover" events still apply on iPad and other touch-devices when touching an item. When I want to access the context menu on mobile, I simply touch the target item (as if I was scrolling to it). The context menu button then appears, and I can click it.
robertwilkin tap-and-hold mostly doesn't work as there is initially nothing visible to tap
Not quite sure what you mean "tap-and-hold". You can touch any item as if you are going to scroll, and just like the captions appear (in grid modes) when you touch an item, the context menu button will also appear.
robertwilkin Is there perhaps an optional CSS override to remove the hover feature and simply display the 3 dot menu in the corner of every image?
Yes. Add your own custom css, something as simple as this:
There are of course modifications that can be added for example if you only want the button to appear visible on mobile, or if you want the behavior to differ per layout.