I’m using Alacritty as my terminal of choice on Ubuntu (Pop!OS). When installed manually, it does not work with the hotkey of Pop!OS because you can’t set it as the default terminal.
For that to work, you have to manually add it as an alternative and set it:
sudo update-alternatives --install /usr/bin/x-terminal-emulator x-terminal-emulator $(which alacritty) 50
sudo update-alternatives --config x-terminal-emulator