If you're the same person from that Discord server, we told you the maximum the Switch supports is indeed 2 TB but we also told you that the biggest SD card you could buy is only 512 GB. Just because it supports a certain size doesn't mean its manufactured.
My second point still stands. Also since you're not the same person, I should also let you know that the Switch actually supports a maximum 128 TB SD card. We may never see such a thing in the console's lifetime but if SD cards larger than 2 TB ever come out, you can use them with the Switch.
SanDisk is launching their 1TB Micro SD Cards in April for $450 USD. That'll be the highest commercially available Micro SD card capacity at the time of release. I don't think one can easily justify spending that exorbitant amount of cash on storage, though.
Edit: Micron is launching one as well, not sure if that's coming sooner or later than SanDisk's, or what the difference in price is.