I gate checked bags on LO a few times on bus gates. The agent tags the bag which you take to the tarmac and leave it by the aircraft. Each time the bag was available after exiting the aircraft and not on baggage claim. I have no idea how it work on jet bridges.

BTW regular-sized carry ons should fit into the overhead compartment on all LOT regional jets, i.e. E170, E175 and E190 (they might be gate checked if the flight is full). They will not fit into the Eurolot turboprops.