Hello ovinewar,
Using a browser to log on would likely be the easy way to access the NAS with PC.
You should have the IP address (IpV4) on the phone App.
Open the Settings app for Management Options.
Once you can connect and access the ADM / GUI familiarize yourself a bit then look into:
Set Up with EZ Connect.
"Before enabling EZ-ConnectTM please make sure that you have signed up for an ASUSTOR ID and registered your NAS. Log into ADM using a Web browser. Select [Settings] > [EZ-Connect]. Select the [Enable EZ-Connect Service] checkbox and then click on [Apply]."
https://www.google.com/search?q=how+to+set+up+connect+to+asustor+NAS&oq=how+to+set+up+connect+to...
EZ Connect (AEC) is the Asustor App that will allow you to connect and access the ADM through Windows.
https://www.asustor.com/en/service/downloads/
Select the model of the NAS for downloads.
Check compatibility of the your Drives.
For specific connection step by step contact support and / or search the User Forum.
https://forum.asustor.com/
Simply search for unfamiliar terms / procedure to become more adept with your local network.
Asustor College can be usefull to learn but the Apps make for easy set up and operation.
The RaspberryPi4 and Volumio are less familiar territory for me.
It seems that it would show up on the local network.
But do look into Asustor Apps which may be suitable for use.
High Res Player for example.
Using a browser to log on would likely be the easy way to access the NAS with PC.
You should have the IP address (IpV4) on the phone App.
Open the Settings app for Management Options.
Once you can connect and access the ADM / GUI familiarize yourself a bit then look into:
Set Up with EZ Connect.
"Before enabling EZ-ConnectTM please make sure that you have signed up for an ASUSTOR ID and registered your NAS. Log into ADM using a Web browser. Select [Settings] > [EZ-Connect]. Select the [Enable EZ-Connect Service] checkbox and then click on [Apply]."
https://www.google.com/search?q=how+to+set+up+connect+to+asustor+NAS&oq=how+to+set+up+connect+to...
EZ Connect (AEC) is the Asustor App that will allow you to connect and access the ADM through Windows.
https://www.asustor.com/en/service/downloads/
Select the model of the NAS for downloads.
Check compatibility of the your Drives.
For specific connection step by step contact support and / or search the User Forum.
https://forum.asustor.com/
Simply search for unfamiliar terms / procedure to become more adept with your local network.
Asustor College can be usefull to learn but the Apps make for easy set up and operation.
The RaspberryPi4 and Volumio are less familiar territory for me.
It seems that it would show up on the local network.
But do look into Asustor Apps which may be suitable for use.
High Res Player for example.