What software tools support LDR files?
Pretty much all of the Lego Design tools available support the LDR file format. Usually each tool also has it's own proprietory format for storing design files. Some software I know about are:
Bricklink Studio
Studio is a nice Lego design program developed by bricklink. It supports Windows and MacOS. Bricklink studio produced photo realistic renders and videos (I use this for some of my youtube video introductions),
https://www.bricklink.com/v3/studio/download.page
LeoCad
This is an open source Lego Designer supporting Windows, Linux and MacOS. It is currently an active project with new features being added all the time.
Lego Digital Designer
This software is from the Lego company itself! Unfortunately they have stopped maintaining it, however you can still download and use it. Supports Windows and MacOS.
https://www.lego.com/en-us/ldd