3DPrinting

I use FreeCAD for most of my stuff now, but I found it very, very hard until I watched some video tutorials. After a little training, I'm really happy with it. I tried OpenSCAD, and that can be a really good option depending on your background.

You will also need to choose a slicer, or try some different ones. A lot of people like the prusa slicer, but I've never tried it. I started with the cura slicer, and it worked well enough that I haven't tried anything else. It seems that some people really like the new orca slicer, so that might be a good choice too.

If you can connect a computer to your printer (either raspi, or something else), some software to manage that is definitely helpful. Octoprint is the most popular option, and maybe the only one; so look that up if it's something you think would be relevant for you. There is also something called Klipper for upgrading your printer's firmware. Whether or not that's for a "beginner" depends very much on what their background is, but it's something to consider if the additional features sound worthwhile.

I don't know if these are really the kinds of resource suggestions you had in mind though.

While not open source, Fusion 360 has a free for personal use version if you are wanting a fairly easy to use CAD program. I had been using mostly Blender up until recently since learning how to use Fusion. I love being able to parameterize everything. Blender is awesome though in it's own right. I use both for making functional prints depending on what I'm trying to do. I tried FreeCAD, but it definitely has a bit more learning curve than Fusion.

While not for 3D printing specifically, Andrew Price's donut tutorial on YouTube is a great primer for learning to use Blender and all is basic functions.

Donut tutorial

I actually have used Blender pretty extensively, I was on the Blender forums way back.

I didn't realize I'd be able to use Blender for the modelling because I assumed the sizing would have to be fairly precise.

Excellent! Not something I would've immediately thought of but sounds critical to good prints.

Teaching tech is good
I’d also add troubleshooting guides from all3dp

I would suggest, however, at least checking calibration even if you’re not changing anything- and inspecting it out of the box. (Are the axis square to each other? Is the bed loose? Is the frame? Belts tight but not too tight?) if it’s a lower end… yeah? There’s probably something that needs tightening.

If it’s a higher end printer, well it’ll give you an idea of how it’s supposed to be.

Other resources…

As well as Prusa, this guide in particular, but the community is very helpful.

Also, I’d suggest staying away from thingiverse. A lot of the models are ripped from non-free sourced (like cults3d or my mini factory.); and many of the stls there suck anyhow. Printables my go to.

For more esoteric content… I’d recommend CNC Kitchen there’s always good stuff in their videos, even if it might not be “basic”

Finally… don’t freak out. There’s going to be a learning curve. It’s okay. Take it one print at a time, accept that spaghetti monsters will happen. (Just tell people it’s abstract art,)

Oh actually I never realized that about OpenSCAD. That's sick!

I've used Blender, Fusion360, and Google Sketch. So I'm somewhat familiar with 3d modelling. I guess I was thinking more along the lines of Hardware but Software compatibility is a good topic to cover as well.