For my Lenovo Thinkpad X13 Gen 2, the "Accessible to system" memory reported by mem /v is 2267 MB
And this is a "ThinkPad Ethernet Extension Adapter Gen 2" I am using for Ethernet. The X13 gen 2 and the T14s gen 2 share a hardware manual, so they are very similar.
I also have the Lenovo Thinkpad USB-C Doc Gen 2, so I plan to learn a lot more about USB support under ArcaOS.