But, more importantly, why do you reckon DEQNA would be hard to connect to a modern network? NetBSD still supports it when running on a q-bus VAX: https://github.com/NetBSD/src/blob/trunk/sys/dev/qbus/if_qe....
It has some pretty broken behavior regarding multicast/broadcast traffic IIRC, but nothing putting it behind a vlan or separate LAN altogether wouldn't solve. I've got a little lsi-11 system under my bed I'm hoping to, one day, get the Fuzzball [0] distribution running on. The 22-bit address extension wirewrap the previous owner did needs to be redone entirely, so it's been a "later" project for years now, but I am hoping my little DEQNA will be able to ping the Internet still.
Needs a patched ROM and recompiled kernel, though! See http://www.cosam.org/computers/dec/pdp11-23/20080402.html (and the two subsequent installments)
(That cosam.org site is more what I'd be expecting for a project like this, but maybe I'm just too old and grumpy for my own good!)