It looks like ATR P-72 Gardia di Finanza MM62311 is currently (and for a few days) operating from Lille, patrolling the French-Belgian coast from Le Crotoy to Zeebruges.
Enforcing immigration control policy between EU and Britain ?
Now active along French and Belgium Coast is DH8C TF-SIF Island Coast Guard operating out of Lille. (ADSB)
Between Brugge and ca Abbevile.
So should be TDY here.
TF-SIF is deployed here to prevent illegal immigration across the "new" EU border with the UK (as part of a deal with the UK) and was also deployed to Lille in September 2022, for a few weeks.
It is still present, it flew last night again and this morning I saw it parked at the civil terminal, as there's no hangar at Lille that can take a Dash 8.
Other visitors today were:
80/ABY TBM-700 ALAT
Z21121 C-130J-30 Tunesian AF (per adsb)