My Note 8 also stop working after July software update.i updated my software 2 days ago .Same issue with network.No Sim card detected is showing.Unable to open the SIM manager and phone freezes. Tried calling Servcie center, they also suggest the same issue of motherboard change because of IMEI no is crashed.
Need urgent support on this.
Dear Samsung Member,
Greetings from Samsung Customer Support!
We request you kindly visit the service center as your device needs physical inspection. To check for the nearest Samsung service center kindly click on the link: https://www.samsung.com/in/support/service-center/
Thank you for writing to Samsung.
Samsung Customer Support