Yeah, if we can get a full TCP stack implemented, even over SLIP/PPP it would be really neat. I know there was one for SCSI on the MacWorks side, but that would need the SunRem SCSI card.
I wouldn't put too much consideration for ethernet over parallel, it would be pretty slow, though much faster than PPP, and much harder as it would require rebuilding that ethernet box, and then it would only work with UniPlus which is a very limited use case. But worth it only if there's a TCP stack. TCP/IP certainly did exist, the question is was there an implementation for UniPlus? They might have implemented other protocols instead, like Novell's IPX/SPX, depending on what was available in the late 80s, which would mean you'd have roll your own implementation instead, not very easy, though stealing from NetBSD might help.
I do recall that PC Parallel port ethernet devices did exist, I might even have one somewhere, and it's likely it's very similar, though the signals on those and the pinouts are much different. They can't get very close to 10MBps, not that ethernet was efficient enough to get anywhere above 50% - this was the era of HUBs not switches and high collision rates.
If they implemented MAC filtering on the chipset, it might work ok, and likely they had to - (the alternative would be that it would run in promiscuous mode which would send every packet to the driver for inspection and discard the ones not meant for it which would create a very high load on the kernel.)
Off the top of my head, I think the VIA6522s top out at about 650KBps or is it 650Kbps (~10x difference so the case of the B matters), so maybe that might be good enough to reach 50% of the bandwidth of 10BT or 10B2 which would make it workable.
There's a good discussion here, looks like it became available ~1989:
https://www.cisco.com/c/en/us/about/press/internet-protocol-journal/back-issues/table-contents-55/151-25-years-ago.htmlUniPlus has an interesting history, and it was likely also the basis of A/UX. (see:
https://en.wikipedia.org/wiki/A/UX where it mentions UniSoft ported it for Apple) So if we can find the source code to a later Unixen than was related closely enough to UniPlus or A/UX, its TCP/IP stack will likely work out of the box. Otherwise early versions of NetBSD (which did support 68k) and the like are the best bets, but it will be an uphill battle. Sadly this doesn't show its full lineage:
https://web.archive.org/web/20170831042833/http://www.graphviz.org/Gallery/directed/unix.svgA word of warning though, please do not put any Unix enable Lisa directly on the internet whether UniPlus or Xenix, whether via ethernet or PPP or just a tty- there are likely security bugs in these old kernels that would easily allow someone to get root easily. At minimum there should be proxy infront of it, and a NAT for outbound traffic. tty access should be proxied via ssh running on another more secure box.