There are some threads of alternatives none of them really good ones.
Some have drilled through I can't remember if it is the lock tumbler or drilled a hole on each side of the housing. You would have to find the thread for the details.
A Member has said you can put say the square end of a 4x4 about 12 inches or so long on what would be the right side of the Truck Tumbler Hosing and have someone stand on the left side and apply a slight upwards life on the trunk lid. You give the end of the 4x4 a smack with say a 2-pound hammer and supposably it will unhook, and the trunk will open because the other person is applying the upwards pressure.
Will that damage the body? I don't know. Better to find the thread on that.
The other method people have used (on a W123) is depending on a lot of things and luck. You remove the first aid kit and if trunk is not full of stuff the get some sort of pole and go through the hole the first aid kit came out of and they remove the plastic cover that covers up the rod mechanism that actuates the trunk lock and is part of the vacuum lock system. Somehow, they deflect the rod and that moves the hook and unlocks it. Again, someone has to be applying some has to apply a slight upwards pressure on the trunk lid.
There is a picture of the opening in post #2
w123 trunk lock stuck-- at my wits end
Post 37 has the direction the rod needs to go in to unlock it.
w123 300d trunk wont open
Another thread:
Trunk lid wont open on '85 300D