Dual-band feed arrangements have been done on dishes used for eme. A classic is 432/1296 feed of VK3UM or similar arrangement 432/2304: crossed dipole feed on 432 with cyl 1296 horn in the center of a large circular reflector plane. But higher in mw wg horn feeds are normal. Hard to get two horns in the same spot (focus).
However, I have a cylindrical wg horn made by W1GHZ which feeds 24-GHz via wg into a smaller diameter wg section opening into a larger section which is fed 10-GHz via wg coax probe. But this is not designed for dual-band duplex operation.
At NASA duplex operation was accomplished using wg diplexers which cut-off RF at a higher frequency thru phasing techniques. 2.115-GHz Tx/2.295-GHz Rx.
Another famous NASA operation used something called a dichroic plate. The plate was put across the mouth of a feehorn so that only 8.4 GHz signals would penetrate the fine holes in the plate but reflect 2.2 GHz. The Plate was angled to reflect the lower frequency to another horn positioned to look at the plate. Of course the dish was 64m in diameter so the subreflector did not have to be small (about 3m to memory). That was used in 1974 for an experiment on MA-10 encounter at Venus.
I believe the 5G/10G sats are being designed with a 1m ground dish as standard. 1m offset dishes are common to the current Direct-TV/Dish Net market. Here in AK 1m to 1.2m dish is std on houses (I have a 1.2m). I also have our old Dish-Net dish which is 1.8m sitting on a pole with nothing hooked up.
Unfortunately, ExHail will not be above horizon in Alaska.