If you have a quick release and you are locking your bicycle in public places, use a hose clamp to secure your seat, wheels, or anything else that could easily be taken. :
Travelwant Bike Seat Post Clamp 28.6/31.8/34.9mm Seat Tube Clip Bicycle Quick Release Seatpost for Mountain Tube Bike Cycling Tool - Walmart.com
Amazon.com: EDOBLUE 2 Pack Bike Alloy Seat Post Quick Release Pin Bike Seat Clamp Pipe Clamp Locking Screws for Mountain Bike and Road Bike Red & Black : Sports & Outdoors
Wolf Tooth Quick Release Seatpost Clamp
Luggage rack for quick release seat tube with leather cover
Ride Out Supply Quick Release Seat Post Clamp (Purple) (31.8mm) - Dan's Comp
Seat post binder Quick Release lever, Stainless Steel – Rivendell Bicycle Works
Mountain Bike Seat Post Quick Release Lever Quick Release - Temu
Bike Seatpost Clamp Quick Release Binder Bolt 43 x 6/8mm Aluminum / Ne – Random Bike Parts
Fixed Bicycle Clip Quick Release Seat Bar Quick Release Bike Seat Clamp Seat Post Saddle Parts for Folding Bicycle Mountain Bike
Black Soft 350 Rl 2.1 Saddle Bag | Scicon Sports
Mountain Bike Seat Post Quick Release Lever Quick Release - Temu
ZTTO Bicycle Parts MTB Bike Quick Release Ultralight Bicycle SeatPost
WHEEL UP C60 Bike Saddle Bag Bike Seat Bag Bicycle Seat Pack Hard EVA Shell Quick Release Water Resistant Wide-opening Cycling Pouch Wholesale | TVCMALL
HOPE 31.8mm QR Seatclamp Red Seatpost Clamp Color Red | Part # | Worldwide Cyclery
Wolf Tooth's New Quick Release Seatpost Clamp - BIKEPACKING.com