Every step below is from an official source
Switch from LastPass to Apple Passwords (iCloud Keychain)
What to do at LastPass before you leave, what Apple Passwords (iCloud Keychain) needs when you join, and everything else the switch touches. Your full plan is built in your browser and stays there.
Official sources reviewed . How we review sources
At LastPass, before you leave
Export your vault from the LastPass websiteBefore
Log in on the LastPass website, open the Account tab, then go to Fix a problem yourself > Export vault items. In the previous layout, go to Advanced Options > Export.
How do I export my vault data while logged in via the LastPass website?LastPass. ReviewedConfirm the export from the verification emailDuring
LastPass emails you a Verify export message. Click Continue export in that email within 10 minutes, then go back to your vault and run the export again.
How do I export my vault data while logged in via the LastPass website?LastPass. ReviewedAllow pop-ups so the CSV file downloadsDuring
After the export, your sites and secure notes show in a browser page. If LastPass pop-ups are not blocked, a CSV file with your vault data also downloads.
How do I export my vault data while logged in via the LastPass website?LastPass. ReviewedNote that TOTP codes are not exportedBefore
LastPass does not support exporting the one-time passcodes (TOTP) you generate inside your vault.
How do I export my vault data while logged in via the LastPass website?LastPass. Reviewed
At Apple Passwords (iCloud Keychain), when you join
Import a CSV file into Passwords on MacDuring
Export your passwords from your old app as a CSV file. In the Passwords app, choose File > Import Passwords from File, choose the file, then click Import.
Import passwords from another app into Passwords on MacApple. ReviewedReview passwords that didn't importAfter
Imported passwords won't replace ones already in the Passwords app. You can review any passwords that couldn't be imported.
Import passwords from another app into Passwords on MacApple. ReviewedDelete the CSV file after importingAfter
When the import finishes, Apple's steps have you delete the CSV file to protect your accounts.
Import passwords from another app into Passwords on MacApple. Reviewed
Then: everything else the switch affects
The steps above are what LastPass and Apple Passwords (iCloud Keychain) say. Your full checklist adds the accounts, codes, payments and devices that depend on your password manager, in a safe order. It's built from your answers, in your browser.