The 3-2-1 rule is wisdom of the ages. The "2" in the rule is all about having your data in at least two different types of "media". A modern read on this is anything tied to the same account counts as the same type of "media". So, you need at least one copy of your data not tied to your Apple ID.

A few things you can do here:

- Own a mac with enough storage to download your entire iCloud / Apple Photos data set. Configure your mac to do so. Your mac is still activation locked to your Apple ID though, so backup that local copy through Time Machine or the service of your choice (e.x. Backblaze). A NAS is very helpful to automate this.

- Use app(s) on your phone that will copy of your data to the location of your choice, such as Photo Sync.