It took me a long time to understand what actually is possible within Renoise.
Have a look at the YT Channel from Hunz, he draws the waveshape for the synths into the Sample section.
https://www.youtube.com/watch?v=essSGWM5ZpU here a vid where he explains the creationprocess. He also offers his old album (search HUNZ album download) as Renoisefiles here in the forums … I learned so much from them.
I myself have underestimated the tools renoise already has ONBOARD, I mean … IT IS already a Synth …
VCFs =>VCA with Envelopes and AHDSRs, LFOs, Effects, Metamixer as other stuff as controlling sources …
so if you use basic waveforms (or basic, clean simple samples of a synth) you have your VCO
And at last: do not underestimate the tutorials Renoise brings on installation … Sidechaining … Maybe Melodies … to me that was mindblowing
And the best thing … if you use those basic samples and only build in tools, ALL is saved in your renoise-file and you can share it AS IS between different Computers … so no panicing should you go back to Windows or Mac or send it a friend … all will sound as you want it
EDIT: for the modular fans => the only plugin I use is VCV Rack (runs on Linux too) to create my own VCO soundsbase, which I then “Render to sample”