Does iCloud work on Linux?
Partly. Apple has no iCloud desktop app for Linux, but the web version works in a Linux browser.
Use iCloud in a web browser
Apple offers iCloud on the web. Open it in Firefox, Chrome or Edge on Linux and sign in. Chrome and Edge can usually install web apps like this one in their own window.
Sources
iCloud on Linux: common questions
Does iCloud work on Linux?
Partly. Apple has no iCloud desktop app for Linux, but the web version works in a Linux browser.