I'm unsure what Flameshot on macOS has to do with Flameshot Linux? I used to use Flameshot on Linux, and it works great, though I've always found the built-in screenshot software for Linux good enough. The application doesn't work as smoothly on macOS and I wouldn't need a tool for screenshots if the built-in tooling was any good. It's like it was designed by someone who had created a screenshot for the first time in their life.