Yeah people affected by this would have to turn on adp (iCloud recovery key) and be vigilant about how precisely Apple chooses to remove that feature assuming the uk government doesn’t back down.
Worst case scenario you’d need to be doing local backups and have iCloud turned off.
Metadata is a bigger worry at that point though.
If the op has their information in emails and doesn’t want to move it somewhere else then pgp is a good way to at least secure those emails a little.
I don’t think it’s a panacea, but as methods of encrypting email go it’s widely supported enough that a person whose private information is stored in email will be able to figure something out.