open the Ledger Live app

then click the gear icon for settings in the top right corner

on the new screen, click Accounts

now go to the row labeled Operation History and press the Save button

select all the networks for which you want to download the CSV file

then click on Save

the requested CSV file will be saved on your computer

in the downloaded file, you’ll find the columns named Account Name and Account Xpub

copy the box corresponding to your public key from the Account Xpub column