I finally got around to tidying up a little shell tool I wrote that turns a network interface you specify into a bridge, and then creates some tap devices with owning user and group you specify and attaches them to that bridge.
This gets around having to run emulated older systems under sudo if you want networking to work.
It’s mostly intended for the PiDP-11/simh, but it also works fine with klh10 and TOPS-20.
Maybe it will be useful to someone else.
Adam