As an iOS + Linux user, icloud.com has been helpful. Access to reminders, notes, in theory messages (I don't use it so can't vouch for it).

The thing to do is to use Chrome (yes...), and open the page. In the hamburger, go to "Create a Desktop shortcut". Choose "open in a new window". This gives you a desktop shortcut to open the page in a standalone way. Visible to your launcher, distinct ctrl+tab... it's janky but I've found this works well.

Firefox please add the Chrome standalone desktop shortcut feature!