[FabHK]

To be fair, Apple has for the longest time allowed export of contacts (.vcard), calendar items (.ics), photos (several formats), music (except for music purchased in the iTunes store for some time that was DRMd), mailboxes, etc.

While I feel locked in to an extent because I don't want to give up macOS/iOS/watchOS and their integration, I never felt that my data was locked up with Apple.

[m0dest]

Apple Notes is different. Notes stored in iCloud (default for iOS & macOS) are stored in a fairly inaccessible local database. They cannot be exported to any format other than single notes as PDFs. The service offers no public API.

[rubatuga]

Although you can transfer them to any IMAP enabled service, and then export them (emails essentially) however you want