Switching ttn-handler-eu to somewhere else


Best TTN users,
Here is my problem with the registration of my RisingHF sensor to my application actually know in the ttn-handler-eu - Automatic Discovery - as I am from Belgium.
With ttnctl I managed to list my applications :

More info on the particular AppID:

In that application there are no registered devices

So I try to OTAA register one with a random DevEUI given by TTN, no problem whatsover:

But now, when I want to set my own DevEUI that is hard coded in the device with 4786E6ED004D002D, it fails:

It looks as if the device was already registered to another application 'temp_sensor". This might be the case because some time ago I once registered this application but managed to delete it soon after.

So I thought my solution would be to change the handler with the same application and register my device there with my hard coded DevEUI. But to no avail:

My question then : can we manually set the Handlers with ttnctl or in the UI-console so that there is no automatic discovery involved once we try to register an application?
It seems that European TTN users are automatically affiliated with eu.thethings.network:1904 and so on ... Can I be discovered by, for instance ttn.opennetworkinfrastructure.org:1904 so I can create a new application with my old device ?

Thanks already for investigating.