Just send them the app url and let them know you do private chats on a private messenger. Show them all the fun stuff like stickers, GIFS, groups, stories, etc. Save the delete messages stuff for later.

Pretty sure they log your IP

I think Posteo works for this as well. Could be wrong

Just let them know you don’t want Facebook having anything more on you than they already do. Let them know it has everything people want in messaging apps like stickers (whatever the heck those are?!), GIFS, video and phone calls, groups, etc.

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.