For Illustrator, use CC 2019 to get hi-def display support in the GUI. I don’t use Illustrator much though, so I can’t vouch for how well it works.
Pixelmator on macOS is a good Photoshop replacement.
I got nothing for Lightroom or heavier uses of AE. Or Excel.
Reaper and Nuendo aren't really comparable either. Nuendo just has so much engineering behind it for audio post and multichannel (e.g. Atmos) not to mention expression maps and excellent MIDI editing. I do admit Reaper, if it runs on linuxulator, could work quite well as a prototyping tool on the go. Then again Cubasis and Dorico iPad does it too and can import straight to the Desktop versions.
I do wish there were good open source options but, alas. Maybe some day...
Source: portrait photographer for 20+ years that would ditch Adobe in a heartbeat if it were possible.