Multisite that will display one post on both sites

I would like to convert two sites from HTML with Access database to WordPress, but I need to be able to make a post on one site and have it display simultaneously on the other without reference to the first site. Right now I do this by updating an Access database that both sites pull from. It is ancient and archaic and it’s way past time to get it into the modern world. The sites are https://eaiadventure.com/ and https://ouradventuretravels.com/. Any advise would be greatly appreciated, or if you can point me to an existing discussion, that’d be great!