Now that the new standard became Descriptor Wallet, the Private Key functionality is no longer easely available.
Nothing changed in private keys. It still works and will always keep working. The main drawback is that Legacy addresses need higher transaction fees, but assuming you only use cold storage for larger amounts, the fee is small compared to the amount you store.
Now I have to find another convenient way to keep a paper backup Descriptor Wallet, idealy with QR code, as was previously available.
Bitcoin Core can't read QR-codes. I assume you use a mobile wallet for that, which is still possible with your old Bitaddress paper wallet.