Ledger released some more information yesterday via social media on how their upcoming crypto card will work.
They confirmed our speculations that you won't be able to spend the coins directly from your hardware wallet and the Ledger Live app with the card. You will be required to top up the card by manually sending funds from your LL app to the card's account address. Those coins will then become spendable with the debit card.

https://www.facebook.com/Ledger/photos/a.802170596506829/4746992725357910/