Can the apple watch ultra support hermes leather bands?
Not sure if this is possible?
Yes as long as the Hermes stuff is 45mm as they fit 49mm (Ultra's specs).
From Apple's website: You can match most straps with any Apple Watch Series 3 or newer case of the same size. The 41mm straps work with 38mm and 40mm cases; the 45mm straps work with 42mm, 44mm, and 49mm cases.