Yeah! I love to repeat the meme, but there’s a special grain of truth in it this year. There’s going to be folks fleeing Windows 11, and Mint - in particular - is now such a downright practical option.
I’m too technical myself to comment on how a Linux install goes for non-technical folks.
But it seems like many of us have quietly moved grandma to Linux in the last few years and she was happy and successful using it.
I’m going to deviate a bit from your question, since you asked a bunch of questions, and aim at the implied question underneath: “is there any hope for a non-expert?”
A Synology network attached storage device (NAS) provides reasonably good answers to the question “how can I have privacy and have some backups” without being a Linux expert.
It ships with apps that replace common cloud services with local backup equivalents.
It can also be configured to do local encryption before backing up to a cloud service, for data where disaster resilience is more critical than privacy (i.e. a library of family photos).
Edit: And as others have explained - we must always remember that the cloud is just someone else’s computer.