Every step below is from an official source
Switch from Apple Passwords (iCloud Keychain) to LastPass
What to do at Apple Passwords (iCloud Keychain) before you leave, what LastPass 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 Apple Passwords (iCloud Keychain), before you leave
Export all passwords to a CSV file on MacBefore
In the Passwords app on your Mac, choose File > Export All Passwords to File, click Export Passwords, then choose where to save it.
Export passwords from your Mac to a fileApple. ReviewedKnow which passwords can't be exportedBefore
You can't export Wi-Fi passwords, passwords shared with a group you didn't create, or access to Sign in with Apple accounts.
Export passwords from your Mac to a fileApple. ReviewedTreat the exported file as unprotectedDuring
Exported passwords are not encrypted. Anyone who can open the file can see them.
Export passwords from your Mac to a fileApple. ReviewedDelete the file after importing elsewhereAfter
Once the passwords are in your new password manager, delete the file you exported.
Export passwords from your Mac to a fileApple. Reviewed
At LastPass, when you join
Use a generic CSV if your manager isn't supportedBefore
If LastPass's on-screen import steps don't support your current password manager, you may be able to import a generic CSV file. Check first that your current manager can export to CSV.
How do I import stored data into LastPass using a generic CSV file?LastPass. ReviewedMatch your CSV columns to the LastPass templateDuring
Column titles must match LastPass's sample template. The columns are url, username, password, extra, name, grouping, fav and totp.
How do I import stored data into LastPass using a generic CSV file?LastPass. ReviewedUse passive import if your manager can't exportDuring
Run LastPass alongside your old password manager. Visit each site, let the old manager fill in your login, then add it to LastPass.
Then: everything else the switch affects
The steps above are what Apple Passwords (iCloud Keychain) and LastPass 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.