Gnome tweaks and dconf say right-click resizing should work. It does, but only with the touchpad buttons. If I use my Logitech G603, it refuses to cooperate. Took a while to figure out why, so I’m sharing in case someone else is banging their head against the same brick wall.
Turns out, the Logitech G603’s right click triggers both BTN_RIGHT (273) and BTN_EXTRA (276) at the same time. A normal mouse would just use BTN_RIGHT, with BTN_EXTRA reserved for a separate physical button. Apparently, Gnome can’t handle this kind of messy double-input nonsense and blocks right-click resizing, which is mildly infuriating. I've tried this mouse with three different Linux computers, and the result is always the same. This is clearly caused by the mouse, not the system.
Side note: I absolutely love that sort of smooth resizing. If you haven't used it yet, I highly recommend trying it out. I can’t believe how Windows users live without it. Imagine trying to aim for the 1 pixel wide edge of a window every time.
Anyway, if you’re running into the same issue, check what your mouse is actually sending when you right-click. Install libinput-tools and run:
sudo libinput debug-events
My output looks like this:
event7 POINTER_BUTTON +1.688s BTN_RIGHT (273) pressed, seat count: 1
event7 POINTER_BUTTON +1.688s BTN_EXTRA (276) pressed, seat count: 1
event7 POINTER_BUTTON +1.935s BTN_RIGHT (273) released, seat count: 0
event7 POINTER_BUTTON +1.935s BTN_EXTRA (276) released, seat count: 0
As you can see, a single right click produces four lines corresponding to pressing and releasing two buttons. If I can disable the BTN_EXTRA (276) input, I’ll stick with my Logitech. If not, I'll probably switch to one of my backup mice.
I'm planning to test those later this week. Hopefully, they know how to behave. Next time I'm buying a (used) mouse, I'll definitely test it this way before paying. I don't want my hardware to require extra troubleshooting just to do basic things.
I'll be looking into that tweaking side later as well, now that I know what to look for. If you have any tips, tricks, and sources to check, feel free to drop them in them here.
Update: G305 and Corsair Harpoon RGB Wireless Gaming Mouse don't mess around with the clicks like that. Those have a completely normal right click. Only the Logitech G603 is doing something weird here.