There seems to be premlimniary support via the open source radeonhd driver, but so far it has crashed for me on my 740G chipset board.
I was able to get the ATI Catalyst driver to work with my RADEON 2100. Although it is not listed at the ATI/AMD webpage, the driver does recognize it as a 3rd party board, and allows you to use it. But don't expect any great speed yet.
(II) AMD Video driver is running on a device belonging to a group targeted for this release
(II) AMD Video driver is signed
(II) Module fglrxdrm: vendor="FireGL - ATI Technologies Inc."
compiled for 220.127.116.116, module version = 8.56.4
ABI class: X.Org Server Extension, version 1.1
(--) fglrx(0): Chipset: "ATI Radeon 2100" (Chipset = 0x796e)
(--) fglrx(0): (PciSubVendor = 0x1025, PciSubDevice = 0x0155)
(--) fglrx(0): board vendor info: third party graphics adapter - NOT original ATI