Re: 12 word BIP39 backup: backup of private Keys still needed?

You can restore all bitcoin address you have only with 12 word mnemonic, so it's not necessary to backup all the private keys. You better make sure to backup/remember those 12 words instead.
But, backup the private keys if you still feel anxious Roll Eyes

Hello, can you give an example of a situation when BTC owner MUST have private keys? In other words, a situation when 12-word recovery phrase won't be sufficient?

For forks. Not all seed-protected wallets support exporting private keys, e.g. Ledger Nano S.

With the seed, you can still generate all the private keys that the Ledger Nano S will ever use.