We already have the package 'doublecmd' in the shannon Solus repo. This is the GTK-based version of this tool.
Now, with the Solus-Plasma release, it would be fantastic to have this tool in Qt5-based version.
And it will be ready for the future Qt-based Budgie, whenever it comes...
It is FOSS, of course.
More info with links to source code at https://doublecmd.sourceforge.io/