OMSI 2 is notoriously finicky. Payware maps rely on specific object libraries and splines. Pirated versions almost always come with missing files. You will likely spend hours fixing "Fehler bei Bereichsprüfung" (error checking range) messages only to find the map loads as a blue void.
File-sharing sites that host "free OMSI 2 add-ons" are notorious for bundling malware, adware, or trojans. Downloading a .exe file from an untrusted source claiming to be "Saint-Servan free" is a fast way to infect your PC. omsi 2 add-on saint-servan free download
The paid version of Saint-Servan (usually sold via the Aerosoft launcher or French sim shops) costs around €15-€25. Steam sales may not cover third-party French maps, but keep an eye on Aerosoft’s weekly deals. Waiting for a sale is safer than hunting for a cracked file. OMSI 2 is notoriously finicky