Some people have this error:

W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://dl.yarnpkg.com/debian stable InRelease: The following signatures were invalid: EXPKEYSIG 23E7166788B63E1E Yarn Packaging <[email protected]>
W: Failed to fetch https://dl.yarnpkg.com/debian/dists/stable/InRelease  The following signatures were invalid: EXPKEYSIG 23E7166788B63E1E Yarn Packaging <[email protected]>
W: Some index files failed to download. They have been ignored, or old ones used instead.

This command will help you to solve this case

curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add -