I personally like Affinity Designer and have designed quite a few things with it. They are behind illustrator on features, I can't deny that, but I've been able to find answers to everything I needed.
Also they have solid developers working on the app. Check out this technical explanation of performance improvements to their rendering pipleline:
For a photoshop replacement, however, I would say Krita hands down. Again, its not as polished as photoshop, but I prefer it over Photoshop at this point even with all its rough edges. I really need to make a video or something about how to set it up and use it correctly but I think its got a lot more going for it.
Krita is closer to a Photoshop competitor than Illustrator. Inkscape is like Illustrator but honestly it is not very good, mostly due to seriously poor performance.
I don't know if Atril is a good Acrobat Reader replacement either. Does it support PDF forms and annotation? That's what most PDF readers are missing.
Apple's preview is pretty great from that point of view. I've also used Xournal++ for that in the past.
Yep -- Inkscape might have some advantages in exporting SVG to FreeCAD, too -- I've seen some differences with Affinity Designer that I don't quite understand.
Lately I've just been using Microsoft Edge for viewing and filling out PDFs. It has the handy ability to draw on and sign documents. That's about all I used Edge for.
At least for amateur/hobby work, I've used the following for years and love them. I also try to regularly donate to them.
Instead of Illustrator for drawing, use Inkscape https://inkscape.org/ and/or Krita https://krita.org/en/.
Instead of Lightroom for developing digital photos, use Darktable https://www.darktable.org/
Instead of Photoshop for touchups, use GIMP https://www.gimp.org/.
Instead of Acrobat Reader, use MuPDF (mobile) or Atril https://wiki.mate-desktop.org/mate-desktop/applications/atri... (Linux)