OP6T update OOS, TWRP

- Download on phone Magisk.zip and twrp-fajita-XXXX.img
- Update from official system update
- enable usb debugging from options
- reboot into bootloader
- fastboot boot twrp-fajita-XXXX.img
- from twrp 'Advanced -> Install Recovery Ramdisk' and select twrp-fajita-XXXX.img
- from twrp install Magisk.zip
- wipe cache
- reboot

UPDATE lineageOS
download lineage on /sdcard/Download/
download twrp install zip on /sdcard/Download/
download Magisk apk on /sdcard/Download and rename it into .zip
reboot to twrp
intall lineage and twrp, clean dalvik
reboot to system, but press vol down to enter recovery (it will boot on the new slot)
install Magisk.zip
reboot system


fastboot boot twrp-3.3.1-1-fajita.img # doesn't work with more recent versions
adb push twrp-install-latest.zip /mnt/
Install zip from TWRP
install twrp
reboot system

Install TWRP:
- reboot into bootloader
- fastboot boot twrp-latest-fajita.img (if doesn't work, use a older version of TWRP, pres vol up + power to turn off)
- Enable ADB sideload from TWRP
- adb sideload twrp-installer.zip


Both slot A and B should have the most recent version of OxygenOS installed, get it from XDA, guides, news and discussion section (updates drivers, UEFI, etc, otherwise lineage might not boot)
Reboot into TWRP, see above if not installed
Enable ADB sideload from TWRP
adb sideload lineageos.zip
adb sideload twrp-installer.zip
reboot