Motherboard for Macbook Pro 2015 model

In many parts of the world, older used Macs end up in MacBook Pro "junkyards" in the hands of fixers willing to take five apart to get three working.

Their main business is, you send them your broken Mac, they fix it with used parts, and return it to you.

I recommend you look for a service like that, available to you.

In the U.S., dealers like

https://www.powerbookmedic.com

... have been doing this for so long, even their NAME is obsolete.

Caution: working inside these MacBook Pros is VERY complicated without substantial training and experience. You are FAR more likely to make the problem worse than to fix anything.

Since that 2015 MacBook Pro is considered obsolete by Apple, no new motherboards are being manufactured for that Mac, and no Apple Store or Apple Authorized Service Center will likely help you install a used replacement motherboard if you can find one.

If this were my Mac, I would simply replace it with a new[er] MacBook Pro and particularly one that could receive current updates and be eligible for service.

You will need to do a web search for that sort of part. No one here can sell you one.

Regards.