Earlier quoted context omitted.
The DPT-RP1 line was acquired by Fujitsu and is now sold at the Quaderno. The hardware has been updated a bit in the Quaderno Gen 2, including a Wacom digitizer. They're still great devices, and the same open source software for the DPT-RP1 (dpt-rp1-py) works with both Quadernos.
It's been awhile since I've looked into it, but are you sure the open source software is compatible with the latest Quaderno's? I've been following this issue[1] on GitHub that seems to suggest people are still holding out for a solution. [1] https://github.com/HappyZ/dpt-tools/issues/181
I have a Quaderno Gen 2 and personally use dpt-rp1-py (https://github.com/janten/dpt-rp1-py), so I can confirm that at least it works. (When I first set it up, I had to run the "dptrp1 register" command twice because I got an error message the first time, but that hasn't come up again -- you only have to register it once on a given computer.)