We seem to be in an unfortunate situation: booting without 'nomodeset'
causes hangs when booting on some NVIDIA cards (6948c3ab80), but on the
other hand adding 'nomodeset' prevents X from starting on other hardware
(e.g. issue #10381 and my Thinkpad X250 with an integrated Broadwell GPU).
Attempt to remedy this situation a bit by adding a separate entry in the
ISOLINUX menu (with the non-'nomodeset' being the default).
269f261c73