Technology

With GIMP 3.0 it's a bit better at least, they've finally added non-destructive editing:
https://www.youtube.com/watch?v=qfaq-Cm1ZkA

Full changelog here:
https://www.gimp.org/release-notes/gimp-3.0.html

I'd dare say that unless you've already learnt Photoshop (and have to unlearn it) then Darktable+GIMP works fine for home photo editing.
If you're used to Photoshop and your skills with it is what puts bread on the table... then I completely understand not switching tools.

The same with Lightroom sadly. The open source alternatives are either too buggy or have UX designed by very "opinionated" people, making them painful and frustrating to use. I currently want to get rid of Lightroom but can't.

I use krita way more than gimp

I love love love GIMP!!!

But yeah it's not a PS alternative, and tbh that's not really what it's supposed to be or what its developers want out of it. it's different

Browser is nice. On Linux though, Okular is superb (except for its occasional problems with forms).

Yeah the PDF category is weird / lacking. LibreOffice Draw and Inkscape can both edit PDFs and are missing as well. Xodo looks like some mobile app only or SaaS product.

Edit: Xodo does have a free desktop PDF reader but seems like they're certainly focused on selling their subscription based PDF editor

Firefox can do basic annotating, adding text and adding pictures but it can't make a new PDF from scratch.

You may be confusing Adobe Acrobat Reader with Adobe Acrobat? Full Acrobat is the proprietary tool to make a PDF file from scratch including some of the more complex functions.

PDF is an open standard and has been for a while, so there are now plenty of alternatives for most of the functions. LibreOffice Draw and Inkscape can do a lot of PDF creation functions but not all. There are also "print to PDF" options to create basic PDF documents too.

However some of the more niche functions are not widely supported or well supported; and there isn't really any opensource dedicated PDF maker that I'm aware of. Layout tools are abundant but I think it's things like building forms and document signing that is less easily replicated. There is Master PDF - a fully functional PDF maker which is proprietary and available for Linux; it $80 for a perpetual license. I'm not aware of any other alternatives myself.

Adobe acrobat is THE PDF editor. PDF is a proprietary format created and developed by Adobe. Any software that can edit PDFs is doing so in a format they do not have any control over. And there just aren't any proper PDF editors that are feature complete. now if you're an individual who needs to make a PDF in the privacy of your own home, by all means, use a cheap or free or FOSS application to do so. But if you need that PDF to be readable and useable and seamlessly compatible on other computers for other users for ever? Better pay the Adobe tax because there is a good chance, it won't look the way you expect it to when someone opens it up in Adobe which their company definitely has.

I've never used vector programs. What is a "live tracer"?

I've spent the better half of six months trying to answer this question. (not continuously, just passively)

For some background, I used fusion 360 for a number of years, so I witnessed it turn to absolute shit, but that means parametric CADs are my cup of tea.

Here's my thoughts.

FreeCAD: I tried this, but I'll admit I gave up quickly.
It doesn't feel like a complete solution. It feels like more and more tools have been tacked on without the realisation that people who haven't been using it for years are going to have even less of an idea of where to start.
I do want to come back and give it another shot, as it hit 1.0 recently.

Plasticity:
I was originally interested in it because if how easy it could be to model something. After having used it for a number of days, I agree that it's relatively intuitive to get something going, but it lacks the precise feeling of a parametric CAD. Don't get me wrong, you can be precise with it, but it feels something akin to a 3D paint and less like a CAD program.
I can imagine if you just want to do something small, it would be sufficient.

OpenSCAD: I've been a programmer for 15+ years, and I expected to like this.
Sadly, if you lack a strong maths background, you'll find this difficult to master.
I'll be the first to admit my maths isn't as great as it used to be.
The beauty of a parametric CAD is that I don't need to know how to position everything exactly, I can just give it the constraints and it manages it for me.
With this, it felt like I kept on testing a value, measuring the resulting dimension that I was trying to go for, tweaking it again, rinse and repeat.
Didn't feel like I was programming, it felt like I was writing the 3D model itself with a DSL.
The lack of fillets and chamfers was also frustrating.

And this brings me to my current recommendation:

SolveSpace:

I've been using it for about a month now, and I've been happy with it.
It didn't take much to understand what it's trying to do.
It's completely parametric and I felt at home pretty quickly.
You can do fillets and chamfers easily, it just requires a bit of creative work.

Let me know if you have any other questions.
I'd be happy to answer them.

I am surprised that its actually still a product they sell and seemingly update. Looking on their product page, wow it has git support - it can be yours for $22.99/month too!

(That will also require you to give your soul to them too, via a contract signed in blood)