How to upgrade to iCloud+ using Linux or Android?

No, it doesn't appear, as also stated in the Apple support pages, because it's a "iCould Web-Only" account, which is what you get if you make an account not using an iPhone, iMac, etc. I was thinking that upgrading to iCloud+ could fix that, but haven't been able to verify that it will add the calendar. The trouble is, it doesn't seem to be possible to do the upgrade using a Web-Only account. It would work from an iPhone, but if I had an iPhone, the upgrade would be redundant. Quite kafkaesque.

So I got hold of a Windows computer, installed iCloud on that, to have a go at upgrading to iCloud+ to check whether the calendar is amongst the extra features. This is what the Apple support pages suggested for those not using an iPhone or Mac. For $1 it's worth a shot. But when I log into iCloud on Windows, I get the message "Cannot Sign In. Your Apple ID must be used to set up iCloud on a Mac, or an iOS device before you can use iCloud for Windows."

Apple is the only major home computing company from the 1970's still around, and one got to like it for that, but there is an important reason why nobody in our family owns Apple products, precisely Apple's policy to make their users totally isolated from the rest of the world even in the age of the Internet. It's a gamble. Microsoft also tried that, but even they eventually made a 180 degree turn. When will Apple turn around or fall?

Sigh.

The steps don't work, since the calendar doesn't appear in a web-only account. See Get more iCloud features - Apple Support: "If you sign in to iCloud.com using a web browser on a computer and only see Contacts, iCloud Drive, Keynote, Notes, Numbers, and Pages, you’re using a web-only account." It also says that more features (in addition to more storage) are available with iCould+, but doesn't specify whether that includes the calendar.

So the question remains: How to get access to the calendar feature if you don't own any Apple products? (or Windows, for that matter)

Borrowed an iPad. Logged in on icloud.com, but not possible to upgrade to iCloud+ using Safari. And iCloud can't be installed or configured because it's a school iPad managed by the school. Sigh again. Such a simple thing has become incredibly difficult.