Best you could do:
1 - buy Amazon gift card with crypto
2 - brand new fake amazon account
3 - buy the kit on Amazon, deliver to PO Box or amazon locker
4 - create fake 23am account, disagree to every single sharing thing possible, spit, send the kit back
They’ll still share it though, and if they do want to find out who you are they can, at least your family name by cross analyzing your dna with your not so distant family members that also did the test