There are two separate issues here:
- Fact the FSDT Updater hasn't automatically detected some 3rd party airports. Assuming you clicked the "Exclude 3rd party" button AFTER you installed these, the most likely reason why they haven't been recognized is they might have package names not confirming to the standard convention of developer-airport-ICAO-name, but that's seems strange, since all Marketplace products are supposed to be named like that, so just be sure you ran click the "Exclude 3rd party" after installing these sceneries. However, then can always be disabled manually, by typing their ICAO code in the Search box and move their Jetway replacement file to the Disable column.
- You think not seeing the GSX replacement jetways at LIRF is a problem. Quite the opposite: it's EXACTLY how's supposed to happen, and what SHOULD have happened if even the other airports were Disabled automatically. That's what "Disabled" means, a 3rd party Disabled airport won't have ITS OWN Jetways replaced by GSX, that's what the Disable column is used for.
Because this is the main point you probably are missing: GSX is not supposed to replace Jetways on 3rd party airports! It might be able to do that, visually, but it will never work properly, because the set of Jetway replacement files that comes with GSX are designed only to replace jetways on DEFAULT airports, since they contain exactly the same parking spots and exactly the same Jetways in the same position as they default airport they are supposed to replace.
If you use a 3rd party scenery, it will come with its own parking spots, which will likely have different names and positions, so if you add a GSX replacement file made for the default scenery positions, it's very likely they won't work. We left the users a choice, because there might be some cases where an add-on scenery was made as an enhancement of a default airport, so it might work with the jetways replaced, but in the vast majority of the situation, you MUST Disable an airport from GSX jetway replacement, if you have a 3rd party scenery for that airport.