This is an issue that does not need to be solved - just posting in case anyone comes across it.
Backup FreePBX 14 / Asterisk 13 ----->>>> Restore to fresh FreePBX 15 / Asterisk 16
Extensions are Chan_SIP on FreePBX 14
Restoration appears to go well
However when accessing SIP Settings, the error/debug screen comes up with
Invalid argument supplied for foreach()
Result was upgrading that module to the Edge version using the following
fwconsole ma upgrade sipsettings --edge
…looks like someone has resolved this already (although I could not spot it in the bugs list)
Just posting in case you come across it.