I should think you could probably freeze it if your freezer can hold a consistent low temperature (don’t use an old one that’s likely to vary the temp or build up frost).
Some of the vitamins may lose a little of their nutrition but it would keep the powder safe to consume.
Make sure you seal it in clean airtight containers first.
I’ve frozen huel after making it with water and that stored surprisingly well - so I should think the powder should be ok to freeze too.
@JamesCollier might be able to comment on any possible nutrient or vitamin loss. Some of the nutrients might be less stable at low temperatures (?)