Unfortunately, there is no ETA yet. Currently the console version patches are being prepared to start the submission process (that is much more involved than updates on PC).
You could temporarily swap who is hosting, if at least one of your friends is playing in Windows, or on a Mac where this is not an issue.
Each save is a folder in the '~/Documents/Larian Studios/Divinity Original Sin 2 Definitive Edition/PlayerProfiles/<ProfileName>/Savegames/Story' folder.
For the App Store version, the path is: /Users/<UserName>/Library/Containers/com.larian.dos2/Data/Documents/Larian Studios/Divinity Original Sin 2 Definitive Edition/PlayerProfiles/<ProfileName>/Savegames/Story
