My situation is this: my rigs are in a closed rood with only two vents for AC coming in.
AC is stuck at 20C/68F.
The room is closed: no windows and no way for the air to get out.
The room also cannot be modified, since it's not my house and the owner has refused any modifications I proposed.
...
...
The obvious solution would be to convert one of the two aircon inlets into an outlet. Might be very easy if you are handy, or a complete disaster if it goes wrong.
But as others wrote already, you need to let the heat out, somehow.
How about a few extra washers placed on the door hinges to lift it off the floor to create a leak?
What is above the room?
If you have a quality wood door.
Say like this:
https://www.homedepot.com/p/Krosswood-Doors-32-in-x-80-in-Rustic-Knotty-Alder-2-Panel-Top-Rail-Arch-Solid-Core-Wood-Stainable-Interior-Door-Slab-AE-1213280SLB/202980361
and access to a proper circular saw like this :
https://www.homedepot.com/p/DEWALT-15-Amp-Corded-7-1-4-in-Lightweight-Circular-Saw-DWE575/203273038
you could remove ½ to maybe ¾ inches from bottom of the door.
Good luck fixing the heating issues.