@aral @aadilayub On all these desktops app icons are expected to be installed to:
/usr{/local?}/share/icons/$theme/$size/apps/$reversedns.png
/local is optional, $theme is the icon theme it caters to, $size is how many pixels it is tall & wide, & $reversedns identifies your app. A variety of image formats are supported, though I usually see PNG or SVG.
Any "Linux" app will install an icon to the "hicolor" theme which is the standardized fallback, though it recently doesn't have to be that.