Hi Sh4pe, welcome!
I think this is the same as what was discussed here: How to find which package dependency it is?
In that case it was Logseq, but it could be a different package for you.
Mixing stable & unstable is a common topic discussed. Recently here: Mixing stable and unstable packages on flake-based NixOS system. You might need to use stable for the package that has the electron dependency.