wifi not working - preliminary causes

i'm considering procuring an iphone 7 with the issue of "Wifi not working, won't connect to a wap/hotspot". i'm taking a flyer on it. if it's well and truly unworkable, i can gut it for parts. however (as long as the icloud is off) i always take a shot at trying to rehab/resurrect a phone with issues.

if all you know is "the phone works, but wifi doesn't" what are the chances it's an antenna or some sort of non-motherboard component that needs to be swapped out vs something on the motherboard? i will do component level swaps, but i have neither the tools nor skills to do microsoldering or chip level repairs.

first thing i'll likely do is pull the motherboard and drop it into a iphone 7 back housing (with all known good parts) and crank it up. i'm just curious about what expectations i should have regarding this wifi problem. for example, if it's 100% a motherboard issue, i might give let it go, but if there's a (fair to good) chance that it's something else, it might be worth a shot.

insight and experiences would be most appreciated.