@brnix i faced the same issue yesterday, but with Sway. You should definitely try GitHub - jtheoof/swappy: A Wayland native snapshot editing tool, inspired by Snappy on macOS, you only need to get the packages grim, swappy and slurp, and then the command grim -g "$(slurp)" - | swappy -f - (Just bind that to a keybinding for example).
I have to say that I even like it better than flameshot.