Kids pick these things up really quickly, and like Minecraft, building Lego is also really very creative and relaxing. The biggest problem is all the choices there are, as they all work a bit differently.
An interesting online option is MecaBricks, and downloadable options are Lego's own Digital Designer (LDD) which although no longer supported can still be downloaded from their site. Other offline options are Bricklink's Studio, and LeoCAD. Although all are Windows and / or macOS, I've tried two on Linux with WINE Bottles, and they run just fine.
See an article about some options at
Rebrickable Help Guide: Virtual Building - A General Introduction | Rebrickable - Build with LEGO#
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Rebrickable - Build with LEGO
