RuhNet

Yealink has an XML developer's guide that is freely available (just Google search and find the latest version, or one that matches your firmware version). You can check it for info on how to modify the XML so that it works properly.

The problem with some of the Cisco phones that I've had (the ones designed to be used with Cisco Callmanager, not the SPA series) is getting them to register to a domain, rather than an IP address.

Anruag, if you paid via credit card or PayPal, you may be able to reverse the transaction.

Yes, you can use the TFTP Recovery method to put a stock firmware back on the phones. (Just Google "Yealink TFTP recovery".) You can actually do the process without using a TFTP server if you wish, by putting the files on a USB thumb drive. Either way, you hold down the speakerphone button while the phone boots up and you'll be presented with a simple menu where you can load the recovery files.

Ah ok; that's much clearer information. I checked on those specific gateways, and they appear to be versatile enough to do it several ways. The easiest way would be to give each gateway a static IP address, disable registration, and use user/password authentication to select the proper outbound channel, and set your Kamailio server IP as the outbound server address. Then setup the "trunks" as regular outbound carriers in Kazoo, with user/pass, and add the gateway's IP to the carrier ACLs on your Kamailio servers to allow incoming calls. You may also be able to mess with some settings in the gateways and avoid using individual credentials for each line, and use a single credential for each gateway, and have a ring group or something within the gateway select a free outbound line.

Well, yes, I and probably others have experience with this but there are many many different multiport gateways, all with various ways of being setup and with various features/limitations/etc. So, more detail is needed before a useful response can be provided. Are you working with a specific brand/device you are having an issue with, or looking for recommendations, or ???

What are the types of issues that v85 firmware is causing?

You might find this link helpful. Although it's for AWS, the same config (at least mostly) would apply to Azure. https://github.com/OpenTelecom/kazoo-install-guide

Gagan it looks like you are missing the "register" string in sip.conf. A look at your kazoo logs or SIP trace when you try to send a call from Asterisk into Kazoo would confirm, but it looks like with what you have, your Asterisk isn't actually trying to register. To have it do that, you need to have an additional line in the [general] section of sip.conf like this: register=>SIP_ID:Password@20201126085320.sip.XXXX.com Also you have "nsecure" where it should be "insecure" 😄