Might be obvious to some this one.
When I get around to removing my EGR, ( yes, yes. I know)
Would the blanking plate be a reasonably sensible place to locate the probe
For the EGT gauge that currently sits , redunantly, where the stereo was.
( alongside the boost guage that is also redundant as soon as you put anything in the cup holder)
Seems like a really easy place to mount a boss to without any faff

Thats where I would stick it easy to dril a hole and tap the blaning plate or weld the boss into the blanking plate