Somehow I was able to boot / via rumpdisk and then the arbiter still worked afterwards, so networking via netdde started working. This is the first time I've had a rumpdisk / with network access!
Alas, I cannot seem to make it work via the arbiter though. My latest attempt looks like the arbiter started but could not give the i/o ports access to rumpdisk: start pci-arbiter: PCI start PCI machdev start Hurd bootstrap pci Copyright (c) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016 The NetBSD Foundation, Inc. All rights reserved. Copyright (c) 1982, 1986, 1989, 1991, 1993 The Regents of the University of California. All rights reserved. NetBSD 7.99.34 (RUMP-ROAST) total memory = unlimited (host limit) timecounter: Timecounters tick every 10.000 msec timecounter: Timecounter "clockinterrupt" frequency 100 Hz quality 0 cpu0 at thinair0: rump virtual cpu root file system type: rumpfs kern.module.path=/stand/i386/7.99.34/modules mainbus0 (root) pci: I/O space init error 22, I/O space not available pci0 at mainbus0 bus 0 pci0: memory space enabled, rd/line, rd/mult, wr/inv ok Damien