Along about 2004 or early 2005, Google Groups started replacing their original user interface with a new one, that they called a beta even as they were rolling it out at their major web locations. The US servers went, if not first, at least close to it; the UK followed not long after. At that time, Usenet enthusiasts started reporting other GG servers that still offered the original, preferred interface. Eventually, someone (thanks!) came up with a link list for 39 such sites. While I don't have a copy of that entire list any more (and now I wish I'd archived it), I offered it here, in this form (links no longer live for obvious reasons):
Those twelve servers were the last ones on the shrunken list to be trashed by the new interface (at least for English); they were the ones that remained after the these two parings based on reports to Blinkynet about the sad demise of the originals.
Sadly, that remaining group were reported downgraded to the beta interface on July 29, 2005.