All great advice, but I personally cannot urge people towards pCloud. I have one of the permanent tiers, but I found the service frustratingly buggy and, when contacted, support was rude and unhelpful. There are so many little odd limitations on the pCloud file system it was frustrating. I also worry that their buy-once business model is not sustainable.

Sync.com provides an even more secure service (zero-knowledge across the board) with similar (better than US anyway) privacy protections in the host country (Canada) that has been, so far for 2 years of use, rock solid (I couldn't go a week without pCloud farting out some error). The subscription model is affordable and generous and the customer-facing pages for sharing files are very professional looking (important to me, because I professionally share files and pCloud looked like a hobbyist page in this regard AND leaked private information).

EDIT: Regarding iCloud. Not only is iCloud end-to-end, but you may turn on zero-knowledge encryption now, as well (Advanced Data Protection I think is what they call it) so that Apple doesn't even have the keys to decrypt your data, making it quite similar to sync.com now.