With root you can flash with EX Kernel Manager, otherwise you need to use TWRP. I recommend fastboot boot TWRP, no need to install it.
change your rom
what rom? I mean Im currently using android 11.
Did you try the current EX version 4.10? Works great for me. I'm on crDroid A11.
You need the latest version, which is always available in the EX Kernel Manager appfwiw, i tried this after not playing with kernels for about 6 months, and heres what i learned
1) ElementalX-P2-4.10 leaves my Pixel 2XL unbootable - luckily i made a backup - so a quick trip to bootloader and then fastboot TWRP and flash the backup kernel image to boot got me back up and running
2) There seems to be no way to get the previous version...4.09
3) When trying the 4.07 version the 1st 3 times i tried off AFH, it reported no mirrors, the 4th time i got a single one...
Maybe it would be an idea to have the release before current on AFH? in case of issues?
4.10 only boot for some ROMs (tried on Fluid & PixelDust)I think you missed the fact the latest, 4.10, bootloops the device?
Leaving with you having to go all the way back to 4.07
Surely having the choice to flash 4.09 is useful?
Especially if youre trying to provide feedback for troubleshooting.
I would think it would be easier for you, if 4.09 was found to be working, to track the changes between 4.09 and 4.10 than 4.07 and 4.10, no?
so that's the reason why.