Frames could be locked up using a chain and a padlock. If you did a cow hitch knot with the chain on the crown of the frame like this:
The lock would have to go through 4 links where the red line is drawn. The end of the chain could be u- locked to the wheel and the fixed object (bike rack or something) or could be run through the wheel, possibly the grab handle if it has a hole, through/ around the rack and then back to the padlock which would mean the lock would be holding five or six links of the chain. Locking a frame up would of course be much easier if you had a Nimbus Oregon, Nightrider/Impulse, a V-frame, or a giraffe with an A- frame. Ultimate wheels would probably be the easiest to lock up; just the wheel and pedals if you wanted.
Edit: This may or may not be possible depending on how much clearance there is between the tire and your frame and how thick the chain is. If there isn’t you may be able to find a chain/lock combo that allows you to lock a loop around a frame leg tight enough that it will not slide over the bearing holder.