With Linux Mint, it’s as I described for the Enter key and for the Return key for Scale... and for Resize Canvas.
I need to click OK. That is the case for the 5.3.1 and the 5.2.16 appimages.
With Windows 10, the Enter key and the Return key both trigger the Scale... and the Resize action with the 5.3.1 installed version.
I see that the Enter and Return key are both used to trigger the Confirm action in the Canvas Input Settings: Tool Invocation group.