Maybe try Spectacle. I use the OOTB Spectacle app on Fedora KDE. It has the same features as Flameshot and is .. well, native.

But on my Mac, I use indeed Flameshot, it's not ideal (the window is "shrinking" when a screenshot is captured), but it's better than any alternative I tried.

Why would you use anything but Shottr on macOS?

I'm not affiliated, but the software is simply on a whole different level. They deserve all the fame.