Given the volume of writing I do, I don’t think hand-writing is feasible.

I write everything longhand. Many people have been writing entire books longhand, and have been doing it for centuries. And a few of us still do ;)

The last few years average out to about 2000 words a day, and most of it is done on computers where I can comfortably type for long periods, and much faster than I could write by hand.

Depends what you want to write, but speed may not be the key elements. Obviously, with tight deadlines from your publisher it may be a valid point but (I'm 50+) along the years I realized I would save more time by writing slowly but then spend less time rewriting/editing (less, as editing is still an essential part).

All of that to say: sure, digital technology may be a great help but it is not a necessity (unlike what big tech want us to believe). Tolstoy did not use a computer, neither did Flaubert, Shakespeare and Dostoevsky, nor did Nietzsche or Plato (to name just a few authors that have written a lot). It's mostly a question of habits, aka developing the hand, arm and shoulder muscles used to write, and of endurance: the more you will write by hand, the longer you will be able to write without feeling too much fatigue. And of organization—aka, how you take your notes and maybe how your organize them. When I draft a text or take notes on the go, something I do every single day of the year, I use my own shorthand which helps me saves a lot of time. I also organize all my notes (research and personal alike) in an analog system that has been formalized many years ago: Zettelkasten. It works wonders and, in its way, it's easily 'searchable'.

One last suggestion: using the right writing tool may help a lot in reducing fatigue too. Have you tried using a decent fountain pen (with good quality paper)? But enough about handwriting :p

If you're using iCloud, have you activated the optional Apple's Advanced Data Protection? It ensures that no one, supposedly not even Apple can read your files on iCloud.

For anything digital (I draft longhand but I still need to type the final version), the moment I became privacy-conscious, my solution was to switch from Mac to a Linux PC, with full disk encryption. With This Linux PC there is no tracking and no telemetry (I was horrified to realize the volume of data that was send back to Apple by my Mac, it's easy to test it: install LittleSnitch and tell it to not let apple's services connect to the web. Sure most of it is probably fine. But probably was not enough for me) and I can use VSCodium (a Microsoft-free version of VSCode) for Markdown and LibreOffice Writer for word processing. For cloud storage, I would suggest Filen.io a small German company that offers zero knowledge end-to-end encryption.

I think many dedicated journaling apps (like DayOne on iOS/Mac) do offer password-protection but I have no idea how reliable it is. I would rather trust some Free/Libre software and the community to tell me what is safe.

BTW, feel free to come say hi to our small !journaling@sh.itjust.works community (I'm the admin). As an analog user myself, I would love to have more digital users participating. Well, to be perfectly honest I would love to have more people participating, digital or not ;)