I received the following error on startup of the game after I modified a list of mods that I wanted to play with:

Failed to load mods: __ProductivityResearchForEveryoneFG__/data-final-fixes.lua:214: attempt to compare nil with number
stack traceback:
    __ProductivityResearchForEveryoneFG__/data-final-fixes.lua:214: in main chunk

A list of mods in use:

* Elevated Rails
* Quality
* Beacon interface
* Cleaned Concrete
* Easy Void
* Enable all Feature Flags
* Factorio Library
* Factorio Standard Library 2.0
* Factorio Planner
* Loaders Modernized
* Milestones
* Mining Patch Planner
* Not Enough Parameters
* Project Cybersyn
* Productivity Research for Everyone (FG)
* Pyanodons Modpack (it enables several Pyanodons mods)
* Range_Buff 2.0
* Waterfill

I found the minimal list of mod to reproduce the issue:

* Elevated Rails
* Quality
* Productivity Research for Everyone (FG)
* Pyanodons Post Processing
* Pyanodons Industry
* Pyanodons Coal Processing
* Pyanodons Raw Ores
* Pyanodons Fusion Energy
* Pyanodons High Tech

Up until I enabled the last mod, ie. High Tech the Productivity Research for Everyone (FG) didn't fail on start.

Oh, yeah, Pyanodons is a MONSTER and should be considered a Total Conversion.
It breaks all the things. My guess is the High Tech addon completely redoes research in many ways.