Sample files are included with the asterisk source code so you could download whatever version you want and extract them. You can also install them if you install asterisk from source and then run make samples. Not sure if there is a way to do that when they are packaged as DEB files.
True. However, they have just been blank by default and there has never been sample versions of them generated. So this is a new thing and not sure why. This could be simply covered in the knowledgebase.
The issue is that the code that generates the config files states that samples of the custom config files exist when they don’t exist. Logically, the way to correct this is to create sample files. I’m not sure that there’s anything to be gained by a metadiscussion of whether or not the code is “right” to say that sample files are supposed to be there, or a debate on whether or not having sample files are a good thing, etc.
The custom files are a requirement to cleanly use FreePBX with ANY optional add on a phone might support that is not part of the de-facto SIP desktop phone standard. For example, remote rebooting of phones - some phones have the ability to reboot if the PBX sends them a command. Other phones have extra buttons like a call record button that are non-standard.
Note that this IS covered in the knowledgebase, for certain specific setups:
While that article dates from a long time ago and the patching asterisk section of it has been superseded by another wiki article, the custom.conf examples in it are still applicable and still needed even if you run FreePBX 17 with the USECALLMANAGER patch. (which the current wiki article on doing that says to back-rev to Asterisk 20 since the USECALLMANAGER patch requires chan_sip which is included in Asterisk 20)
In addition, at one time chan_pjsip also required:
I WILL say though it seems this option is no longer required for pjsip in Asterisk 20 or 21, at least my test 7940s on pjsip seem to register without issue without this option.
However that DOES NOT invalidate the point that the custom files ARE REQUIRED and likely will always be required since there will always be people making new inventions in desk telephone sets and softphone code and FreePBX will lag them. In fact, in some cases (like in the pjsip example) FreePBX -did- support the option in the FreePBX GUI then later took it OUT of the GUI which is why the pjsip custom file became required.