Credits: https://old.reddit.com/r/BuyFromEU/comments/1j9g5h8/i_left_dropbox_as_a_heavy_user_of_15_years/

I had everything in my Dropbox: all my legal documents, my work-related files, my photos from the last 20 years, and things people sent me that I want to look at again when I'm 80… I literally had my life stored in it (and of course locally on two machines and a extra backup disk). I also accessed it almost daily via my phone and uploaded files from my phone.

So, I tested several services in the range of ~100 Euros a year with at least 1,5 Terabytes:

Jottacloud:

• Good Desktop Client (Win & Mac)
• Very good iOS App
• Good service
• Pricey (144 Euros for unlimited storage)
• Downside for me: it doesn't automatically convert photo uploads from my phone to JPG and doesn't store them in a folder I choose – plus, the price is high.

Filen:

• Good Desktop Client (Win & Mac)
• Rough iOS App
• Good service
• Okay price (108 Euros for 2TB)
• Downside for me: the rough iOS App didn't have a document upload with a scan function.

Nextcloud:

• Good Desktop Client (Win & Mac)
• Good iOS App
• No dedicated service; it's Open Source, so some tinkering is required since you manage the hosting yourself.
• Weird price range (Hetzner, the cheapest host by far, offers either 60 Euros for 1TB or 200 Euros for 5TB, nothing in between).
• Downside for me: the price range.

kDrive:

• Good Desktop Client (Win & Mac)
• Very good iOS App
• Amazing service, document editing included, etc.
• Amazing price (60 Euros per year for 3TB)
• Downside for me: none.

So, I chose kDrive, even though I'd love to use Nextcloud because it's Open Source and you can choose your own host. If I needed less than 1TB, I'd definitely choose Nextcloud.

And it should be said that all the services I tested offer free options with a few Gigabytes, if that's all you need.