Freezing sauerkraut for storage does kill off some of the good bacteria and probiotics.
But the probiotics and good bacteria in the sauerkraut is mostly killed off when the sauerkraut is cooked or heated above 106 F.
Some good bacteria and probiotics may survive the freezing temperatures by going dormant however most of the good bacteria will be killed off.
Although freezing the sauerkraut means you'll lose some of the good bacteria in the sauerkraut the sauerkraut is perfectly safe and good to eat.
Although your health won't benefit as much as it would when the good bacteria was in the sauerkraut.
When kept frozen the sauerkraut can last from 6 months to a year.
I freeze extra sauerkraut all the time for later and it's been okay.