Updated phone, now fingerprint & WiFi don't work and I can't read or write from internal storage
After a few days, I figured out the solution for each problem:


Wi-Fi: I needed to delete /data/misc/wifi/wpa_supplicant.conf (which had been restored from Nougat) and reboot
Fingerprint: Delete /data/system/users/0/fpdata and /data/system/users/0/settings_fingerprint.xml
Storage: Wipe storage from TWRP, reboot to OS to reformat it, and restore files from TWRP


For those who would be wondering how to update from OOS Nougat to Oreo, here is a guide.