How do I disconnect all devices linked to my Apple Account?

AFTER you’ve tested operation of your Trusted Number(s) …

Then:

Sign out of your Apple Account and iCloud on your devices - Apple Support

FIRST … Make sure that you have a means to get back “in” !!!

You need to establish a Trusted Number — preferably multiple numbers — other than on your own iPhone.

They can be virtually ANY mobile or voice-only landline phone number to which you can reliably access.

About trusted phone numbers and trusted devices for Apple Account - Apple Support