@KWTPGC yes, this was for me also a question what for it is as I did not read the documentation before using. However, after going to services and enabling SSH access left me thinking what the credentials could be as well as I did think from begin that it is about SSH access to omada controler which was running anyway on a linux with openssh, therefore I simply choose port 2222 instead as I had no clue which ssh server this is. At the end, I asked myself about how do I define access to as example eap's then the lightning struck my brain and I took as possibility that it is configuration for all central managed devices, not for omada controller.

Device account and password are credentials for all your devices, as example if you have a router, go to its page and there you use those credentials, after login you will see a message that device is managed by controller. At the same time this is your SSH access.

With some devices there are issues connecting to them resulting in an error saying something about non existing key algorithm. If you run into that issue, then try ssh with some existing key algorithm which is available on your system, I had this issue with er605 and connect this way:

ssh -oKexAlgorithms=+diffie-hellman-group1-sha1 -c 3des-cbc 192.168.0.7 -p 2222 -l DeviceAccount

In short, those credentials are root access credentials for any service which requires authentification on all centrally managed devices which you adopted.

 Thank you for the reply.  Unfortunately that doesn't help me.  The EAP local login username(s) and passwords are replaced when the EAP is adopted by the OC200.  They are replaced by - to quote - "the Device Account".   So this would be something from the previously working controller settings - but i don't know what those are.  I setup various admin usernames and passwords in the cloud settings of the controller - but these have all been wiped clean by the controller reset.  I have tried them all - on the login screen of the EAP - and none work.  I just need to know what the Device Account was called - is it my Cloud Management login name, is it the name of the controller itself .... The default usernames dont work either.

I really don't want to have to reset each of the four EAPs to factory defaults - as they are all working and the wifi network is used from 7.30am to 8pm each day for tills and other PC devices at our golf club.  It was the controller that wouldn't connect properly after our lengthy power failure at the weekend - due to Storm Eunice.  So, i can get the controller setup from scratch to match the three SSIDs i have working on the four EAPS.  However i can't get the four EAPs adopted by the (in effect new) controller because they think they are managed by a different controller - I am prompted for the EAP username and password, which i believe is this "Device Account" now.

All very frustrating and time consuming....   I think i will have to take the whole wifi setup down by resetting each ceiling mounted EAP one evening - and start again.

  @KWTPGC I am not sure you interpret me correctly. In your omada controller, click on settings and then scroll down to "Device Account", there you can see your username and password as well as you can change those. Those credentials are the username/password for ssh, web interface etc... and yes, even if you log in to web interface it will tell you that device is controlled by controller and you can not set any settings. Of course if you reset, there will be new credentials, if you recover from old settings then your old.

However, those are credentials, just try ssh and see.