How do I know how much RAM my motherboard supports?

Check your CPU instead of the manual. Most motherboards support 32GB as long as the processor does, and nearly every consumer CPU from the last decade handles at least 32GB (often 64GB+). Look up your CPU model on Intel Ark or AMD’s site for the “Max Memory” spec, or run CPU-Z on Windows and check the Memory tab. If your motherboard has two DIMM slots and supports DDR4 or DDR5, 32GB is almost always fine — unless your build is from 2010.