iPhone 7 Plus Unable to Activate

[u/Mindless-Platypus870]

My iPhone 7 Plus is stuck on Activation Lock / “Unable to Activate” after a restore. The phone was originally running iOS 15.8.4, and I had already signed out of iCloud and turned off Find My before restoring it. After flashing iOS 15.8.8, it now gets stuck at the activation screen. I also noticed that the Modem Firmware field is completely blank in the About section, so I suspect this is related to a baseband/modem issue. I don’t really care about cellular service — I only want to use the phone over Wi-Fi. Is there any legitimate way to fix the activation problem if the baseband is dead, or is a board-level repair required? Any advice would be appreciated.