There appears to be no easy way to remap the hotkeys. Add-ons may not be able to modify the native keybindings as on a cursory glance I don’t see any applicable ones on addons.mozilla.org (and haven’t come across any since the Firefox Quantum update).
Add-ons cannot override or replace built-in keyboard shortcuts except by adding code into each page to intercept the shortcut and take whatever action it is supposed to take. Two examples of such extensions are Saka-Key and Shortkeys. They don’t work for all shortcuts; some can’t be overridden by content.