Do you really need a VAT ID though? There is the “reverse charge” mechanism, which IIRC you can use until you sell a lot in any given country. (IANAL)
Both parties having a VAT ID is actually a requirement to be able to use reverse charge: https://vatdb.com/reverse-charge/
It is somewhat annoying dealing with accounting and reporting for reverse VAT as a customer.
Not a dealbreaker in itself, but the sort of little thing you don't want to build a stack of. Shady PO-box address, Yahoo contact email, expired ssl certificates etc.