I second Blender. I don't use anything else and don't see why I would want to. I hope to get into geometry nodes in future.

The donut tutorial is .. handwavy relevant to 3D printing.

3D modelling for 3D printing doesn't require materials, colours, lighting, camera placement etc etc. But doing the donut tutorial will get you used to many aspects of blender and realise just how powerful this software is. It's also kind of a Blender right-of-passage.

The Blender documentation is fantastic if you prefer to learn via pages than random video-build-a-thing tutorials.

Blender tends towards using keyboard shortcuts. Learning them can greatly speed things up.

And Blender has a large body of community forums for questions and answers if you want to search(first), post a question, or likely ask your friendly AI what the answer is.

[edit] the bite sized blender basics videos on the blender.org site no longer easy to find. :-(