Thanks a lot Russell for your detailed answer.
The CalDigit TB3 Mini Dock might introduced a glitch in the GPU management, so an OS clean install would tell if the official USB-C > HDMI apple adapter finally works (solo).
Otherwise the issue seems to come from the GPU or the motherboard...
@DillTheKraut, Russell succeeded to send video through OWC Dock and passive adapter, so an active mini-DP adapter is not always necessary.
Other video technicians told me that the official USB-C TB3 > mini-DP TB2 apple adapter works fine with all their TB2 video adapters.