I managed to get this old controller to work under Rekordbox 5.8.7. It's fully mapped but the Left and Right Jogwheels are inverted. Forward goes backwards and backwards spin goes forward. I know this controller is supposed to work with Traktor but with a little trick it works with Rekordbox too. Under MacOS i just created a new virtual midi device under Utilities > Audio > Midi Studio. Renamed the Pioneer DDJ-T1 to Pioneer DDJ-SX and created a new Virtual Midi device with the same name Pioneer DDJ-SX. Connected the virtual midi out from the T1 to the midi-in on the SX and the virtual out from the SX back to the input of the T1.
Now Rekordbox sees the controller as if it were a DDJ-SX and the Jogwheels now work but the are inverted.
To get the nudge function to work under Rekordbox too i just had to change the PIONEER DDJ-SX.midi.csv a little bit under the section Jogsearch > Jogsearch > Difference to B01F
Now in my midi-monitoring app turning the Left Jogwheel clockwise it values B022 from 00 to 1F and counterclockwise values from 4D to 7F.
From my understanding newer Rekordbox compatible DDJ controllers use values between 70-83 for clockwise and 58-45 counterclockwise.
I'm looking for a way to convert the value input from the T1 Jogwheels. Tried Bome MIDI Translator but as soon as i try to invert te values over in that application there is no way to get them back into Rekordbox...
Perhaps i could open up the T1 and invert te encoders + and - ? as a last resort???