Crossplay? Do you have a like or info or a link on that? I'm very interested on checking that out.
What do you want to know about it? In the server settings you can select to enable steam crossplay or not. If enabled steams clients can join your server also so Xbox and steam can play together. However note that since it is a server with Xbox users on it that it must conform to the Xbox standards so you wont have the full options that you might have on a pc only server. This only applies to Xbox Nitrado servers. Xbox users cannot connect to PC rental servers.