The key to freedom from ecosystems is not to use any cloud/integration systems they're shoving at us. Always use file system. (Using file system sync services like Dropbox, One Drive, GooDrive is fine, because you can switch from one to another in seconds.) I don't use calendar, contacts, notes, reminders apps - I simply do them in platform-independent way. For example, my notes are simply .txt files in dropbox. My contacts are either empty folders named with contact info, or folders with .txt files if there's lots of info in the contact. Same for reminders and calendar. All of these are in my dropbox and I can switch from platform to platform instantly and painlessly. Sure, I don't get notifications, but I just review my organizer every day and keep things to remember in the RAM between my ears.
I use Android, Windows, iOS on multiple phones and tablets, MacOS and Windows on laptops or any computer if traveling, and my organizer is always with me and looks and behaves the same everywhere, because file systems are essentially ghe same, and .txt files are universal.
F the ecosystems! Don't be a stupid fly in a spiderweb.