Hi,
most people dealing seriously with older PDP-11s have found means to
monitor the UNIBUS traffic.
My latest approach is
www.retrocmp.com/tools/uniprobe
UniProbe is a M9302 terminator, a LED display, a probe for logic analyzer.
It can be mounted in Standard or Modified UNIBUS sockets.
I'm ordering a batch of PCBs in a few days and will show this and other
stuff (UniBone, BlinkenBone) at VCFPNW in Seattle.
https://vcfed.org/wp/festivals/vintage-computer-festival-pacific-northwest/
best regards,
Joerg