I would love to see and suggest the following module, that unfortunately I’m not able to programm myself.

Using https://github.com/picklepete/pyicloud it should be possible to download the whole address book and with https://github.com/FoxP/VCF-to-ICS (conversion tested locally, works perfectly) we could create a birthday.ics that can be used with the default calendar module (also tested, working)

{
               symbol: 'birthday-cake',
               url: 'http://localhost:8080/modules/birthdays.ics',
},

In iCloud you can also define an application password for this purpose (login pyicloud) even if you secured your Account with 2FA.

any volunteers? ;)

inspired by: https://github.com/bitte-ein-bit/MMM-iCloud-Client but that is so outdated that you will get 5 serious vulnerabilities installed