Since you don't have TWRP am guessing you are encrypted already
In this case do following
1. Download LOS recovery
https://mirrorbits.lineageos.org/re.../lineage-18.1-20210418-recovery-guacamole.img
2. Now boot to fastboot and run
3. Flash LOS recovery
Code:
fastboot flash boot lineage-18.1-20210418-recovery-guacamole.img
4. Now tap Factory Reset, then Format data / factory reset and continue with the formatting process
5. Reboot to fastboot and do
6. Flash LOS recovery
Code:
fastboot flash boot lineage-18.1-20210418-recovery-guacamole.img
7. Format data again and reboot to fastboot
8. Now download all files from below link (this is extracted crDroid payload.bin - if you know how to use python, can also extract it from latest crDroid zip and help of attached zip)
https://mega.nz/folder/FhUzFCzI#5RoeaGORbfJ1ye68tdZw3A
9. Do following steps in fastboot
Code:
fastboot flash boot boot.img
fastboot flash dtbo dtbo.img
fastboot flash odm odm.img
fastboot flash system system.img
fastboot flash vbmeta vbmeta.img
fastboot flash vendor vendor.img
Note when flashing
vbmeta, you may
not see progress, so let it flash for like 2 minutes and just run
fastboot reboot bootloader to continue flashing vendor
10. From fasbtoot menu, use keys to reboot to system
Once booted to crDroid, you'll be without Gapps and TWRP so lets fix this
1. Install latest Magisk apk
2. Put your boot.img that you downloaded above (or extracted) in your internal storage
3. Open up Magisk and click on top most install button
4. Choose "Select and patch a file", select the boot.img from internal storage and click blue top right "Lets go" text
5. You should now have a magisk patched boot image saved at /Download/magisk_patched_xxx.img
6. Save this file on your PC and reboot to fastboot
7. Flash this file in fastboot
Code:
fastboot flash boot magisk_patched_xxx.img
8. Reboot to system
9. Download latest TWRP installer zip and save it to internal storage on phone
10. Now we have root, so open up Magisk app again and navigate to Modules tab and click on "Install from storage" and from here choose TWRP.zip
11. Now you have TWRP so you can maybe proceed with installing clean from TWRP (as you should have in the first place - see
opening post install clean steps)