I think it's best for countries to allow BTC or any other cryptocurrency while they also use CBDC coin. Allowing people to buy BTC with CBDC app is freedom.
CBDC's and Bitcoin will coexist, countries will go ahead and launch their CBDC's, whilst Bitcoin will still be used by the populace that chooses to use it, I haven't seen not heard of any plan to stop the use of Bitcoin, cause CBDC's are being created, neither of them (CBDC's and Bitcoin) is a threat to the other, Bitcoin is decentralized, the other is not, Bitcoin is about the control and freedom it gives it's users, the other is controlled and manipulated by the government; CBDC's will be a popular thing in the future, but not at the detriment of BTC whatsoever.