There’s plenty of room at the front, I can pop a mountain bike wheel/tyre to check but I reckon 2.0”, maybe 2.1”.
At the rear the seatstay clearance is generous enough, it would be the chainstay area that’ll be the limiting factor. I will try a 1.95” tyre on there.
Could always run a larger front tyre.
Will try to snap some photos with alternative wheels/tyres tomorrow.