I think the bigger question would be what the heat would do to what the trivet was protecting
As for the material itself, I would not use anything with MDF but you could have the design with many sorts of feet worked into the design and even supports above the design, As for veneers, there would bee more delicacy but the glue and pressure holding them on would be as much as the type of wood. In all those cases you would want a good lacquer or varnish to seal the wood as much against stain as anything else.
Acrylic well soften at 300F and might weaken a bit before that but the hot material is rarely above 210F or boiling water. As with everything testing is recommended before making any expensive work be that test,
I’ve figured out a way! Thanks guys! I’ll post pictures once done! I’m using 1/8" proofgrade ply, glued to another non proofgrade ply, with wool felt on the bottom. So far they are turning out pretty nice Not perfect, but I’m ok with that for this round. Less waste, less time involved. Will be ready for Christmas.