So just to be clear, you only need to drop the MATS (and DMAR, and other bothersome tables) if it's in your particular motherboard's firmware. When you say you don't have the drop MATS option in ACPI, do you mean, when you go to ACPI tab, and to the Drop Tables section, and click the "PLUS" sign to add, then click _double arrows_ in the new empty box with double arrows under Signature, and scroll down, you don't see MATS (it's there in recent clovers)? or do you mean your board doesn't have it in firmware (hit 'o' in clover screen)?
But my understanding is that the solution to these "drop MATS and DMAR tables if your firmware has them to prevent backtrace" issues is to, instead, tick 'FixHeaders_20000000' on the Acpi tab, Fixes, tab '2'.
TLDR; don't drop MATS or DMAR, tick FixHeaders_20000000.