If your iPhone has been bricked during the update to iOS 17.3 beta 2:
- Download the iOS 17.3 beta 1 IPSW on your Mac (https://updates.cdn-apple.com/2023WinterSeed/fullrestores/052-20038/3F493ABA-9230-4B7C-9C61-D85B3DC79504/iPhone16,2_17.3_21D5026f_Restore.ipsw)
- Plug iPhone into Mac
- Press volume up, then volume down, then press and hold the side button until the recovery mode screen shows up
- Use iMazing (preferred) or Finder to restore the IPSW (in Finder, hold down Option when clicking the restore button to select the IPSW)
- Your iPhone should be successfully restored without any data loss (see reply!)