It's OK to freeze sauerkraut.
But when you freeze sauerkraut you kill off some of the good bacteria known as probiotics so you won't get all the health benefits from frozen sauerkraut as you would get with fresh sauerkraut.
But sauerkraut does freeze well and is still safe to eat after the sauerkraut has been frozen.
Frozen sauerkraut will last for up to a year and longer as long as it's kept frozen but it won't be as fresh and it's best to consume the sauerkraut within 6 months of freezing it.
The longer you leave the sauerkraut in the freezer the less fresh the sauerkraut becomes.
I prefer to just keep my sauerkraut in the refrigerator and eat it within a few months.
The fresher the sauerkraut the better tasting and more nutritious and health it is.