You can use a couple of commands to get the details of the Office Online server.
The above command will return details about the servers that are members of the Office Online Server farm. These details include the health status and roles held by each server.
Import-Module OfficeWebApps Get-OfficeWebAppsFarm
The above command will return the details about the OfficeWebAppsFarm object.
Example something like below information you will get about OOS server:
The Get-OfficeWebAppsMachine cmdlet returns details about the current server that is in an Office Online Server farm. These details include the roles and health status of the current server and the name of the master server for the farm.
Get-SPWOPIZone | Get-SPWOPIBinding
This example returns a list of bindings that were created on the current SharePoint farm where this cmdlet is run for the zone configured for the WOPI application.
For more details refer to the below MSDN articles:
If you get the “The term ‘Get-OfficeWebAppsMachine’ is not recognized as the name of a cmdlet, function, script file, or operable program.” run the below command:
$p=$Env:PSModulePath $p+=";C:Program FilesMicrosoft Office Web AppsAdminModule" (Environment)::SetEnvironmentVariable("PSModulePath",$p)
Issues with OWA server 2013