There are two ways to use a passphrase on Ledger wallets. The first is as you have described, where the user must first unlock their device with their main PIN, then navigate to settings and manually enter the passphrase they wish to use. There is a second method, however, where the user only needs to enter their passphrase once, and can then attach it to a secondary PIN. If they enter this secondary PIN instead of their main PIN when they first turn on their device, it will open the passphrased wallets without having to manually enter the passphrase.

I don't like this second method because it means you can only use one passphrase at a time, and it also means a user could go years without entering or even thinking about their passphrase, which is a risk since many users do not back up their passphrases securely like they do with their seed phrases.

You can read more about these two options here: https://support.ledger.com/hc/en-us/articles/115005214529-Advanced-passphrase-security