My father has an old landline number that used to be associated with a business he shutdown more than a decade ago, but he puts up a fair bit of resistance when my mother encourages him to cancel it because he insists there are dozens of people who still might try to call him at that number.

Okay, fine. Lets assume that is true.

He recently switched from an old Lumia to a Moto G which has a built-in SIP client. If I port that number to a SIP provider would the incoming calls come through seamlessly? I also note that VoIP.ms discourages using it however it refers to an ancient version of Android.

My attempts to get him to use Google Hangouts for something else were unsuccessful because it took him too long to unlock the screen so I am not inclined to attempting this with a third-party softphone.

Is anyone using this successfully or is it likely just to generate frustration?