Pre-Covid, I got a 9 foot Abus 10KS chain and a lock. That's a 10mm (3/8 inch) thick link. You can buy it by the foot online, with or without the cloth sleeve. It's 16 pounds! I got an inexpensive cloth tool bag from Harbor Freight that is perfect for carrying the chain.

It's for locking two bikes onto my car's hitch rack if we have to leave the bikes for more than a restroom / convenience store stop. I just don't want to have to worry about the bikes on a trip! The built in cable lock that came with the rack can be easily and quietly cut with quality electrician's diagonal cutters. I used a rope to estimate how long a chain to go through both frames and down to the car's towing point.

I keep my road bike in the house, but I'd use a shorter version of this, locked to a heavy floor loop, if the bike was in the garage.