Failed to load mods: Factorissimo2-Playthrough/prototypes/technology.lua:37: attempt to concatenate field 'localised_name' (a table value)
stack traceback:
Factorissimo2-Playthrough/prototypes/technology.lua:37: in function 'create_research'
Factorissimo2-Playthrough/prototypes/technology.lua:48: in main chunk
[C]: in function 'require'
Factorissimo2-Playthrough/data-final-fixes.lua:1: in main chunk

Creative Mod - https://mods.factorio.com/mod/creative-mod
Causing this error. Disable to play.

Failed to load mods: Factorissimo2-Playthrough/prototypes/technology.lua:37: attempt to concatenate field 'localised_name' (a table value)
stack traceback:
Factorissimo2-Playthrough/prototypes/technology.lua:37: in function 'create_research'
Factorissimo2-Playthrough/prototypes/technology.lua:48: in main chunk
[C]: in function 'require'
Factorissimo2-Playthrough/data-final-fixes.lua:1: in main chunk

Are you playing with the mod Geothermal - https://mods.factorio.com/mod/Geothermal by chance, I happen to get that same error when loading the game with This mod and Geothermal enabled together

Failed to load mod "Factorissimo2-Playthrough": Factorissimo2-Playthrough/prototypes/technology.lua:37: attempt to concatenate field 'localised_name' (a table value)
stack traceback:
Factorissimo2-Playthrough/prototypes/technology.lua:37: in function 'create_research'
Factorissimo2-Playthrough/prototypes/technology.lua:48: in main chunk
[C]: in function 'require'
Factorissimo2-Playthrough/data-final-fixes.lua:1: in main chunk

EDIT: I realise now why This mod and Geothermal do not work together so my issue isn't really an issue i was just stupid

This actually is a bug on my end. Will fix ASAP.

Fixed this in 1.2.0. Thanks for the report.