The main SoC doesn't require any proprietary firmware which means the core functionality is freedom respecting, and probably one of the closest things you can get to a truely open phone right now. The primary camera also has proprietary firmware I believe for its autofocus feature. This is out of necessity I believe, as there are no fully FOSS modem chips or WiFi/BT chips out there, so the compromise is to isolate them and allow them to be disabled at a hardware level. Look for multiple partitions next to your SD disk. To see if your SD card is partitioned, right-click Start > Disk Management. To see if your SD card is write-protected, look for a physical tab, move the tab in the opposite direction. Method 2: Camera-> Setting -> Storage -> select SD card as default storage.

Same goes for the WiFi/BT chip, which also runs proprietary firmware. Quickest way: Open File Explorer, right-click the SD drive, and select Format. Method 1: Internet -> Menu (on left-bottom corner)-> Setting -> Advanced Setting -> Default Storage, select SD card as default storage. The modem is separate from the application processor, so even though the modem is running proprietary firmware it has no direct memory access and can be disabled. The board schematics are available AFAIK, and all of the major hardware blocks have killswitches (modem, WiFi/BT, cameras, microphone, headphone).

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