I would suggest an alternative that allows you to use any of the “Big Ones” like iCloud/OneDrive/GoogleCloud/ Dropbox.

Buy Cryptomator on whatever device(s) need access and set up a single vault on any cloud service you use. This vault will be client-side end to end encrypted which means its just you with knowledge of and managing the encryption keys. Put them in your password manager for a while until you memorize.

Remember, if they aren’t YOUR keys, it doesn’t really belong exclusively to you.