When I had a Mac I used an encrypted volume in Dropbox. (Not sure if that's a good idea, but I didn't have any issues.)

I used Notational Velocity in those days :) A rare gem of ergonomics.

Later I did the same thing with a VeraCrypt volume.

Now I'm in Obsidian, which has its own encryption (if you trust 'em!), but never quite got the frictionless feeling of NV back.

The Alternate Notational Velocity (nvAlt) was my go-to for a very long time. https://brettterpstra.com/projects/nvalt/