New setup
In case it can help others, or if people have advice I share where I ended up :
Downloaded trakt history and fed the zip to Floppy (YamTrack fork). Created a SIMKL account as backup.
Installed crosswatch and tautulli and setup :
- webhook for direct update Plex => Floppy/SIMKL
- daily task to sync Floppy/SIMKL=>Plex
I've my setup on my NAS, and a cloud backup just in case. All automated.