Pen not supported, but works in all other modules, but silver Effex is also not supported.
Reason why only viveza and silver efex is they both just had an upgrade while not the other plugin. Send a ticket to dxo support.
I’m still on V2 and the pen works, so it has to do with what they’ve done in V4.
It may not help you, but just to inform that on Mac mini with Big Sur and Wacom Intuos S BT (2018), I have no issue with Silver Efex Pro 3 and Viveza 3 (Nik 4).
This is for both USB and Bluetooth connection.