The main problem when downgrading from OOS-11 to OOS-10 is this:
TWRP 3.5.2 cannot boot with OOS-11, but it works fine with OOS-10. TWRP 3.6.1 works fine with OOS-11, but cannot boot on OOS-10. Also, it can't do a factory reset. Lineage type recoveries cannot flash OOS at all.
So, if you are on OOS-11, you might need TWRP 3.6.1 for initial boot and flashing OOS-10 the first time. After that, boot TWRP 3.5.2 to flash OOS-10 into the second slot. All links are below:
Here is the latest OOS-10:
Download
Here is the TWRP installer 3.5.2:
Download
If you need to load TWRP image to boot the first time, here is the link for the full 3.5.2 image:
Download
Here is TWRP 3.6.1 image:
Download
Rename the TWRP image into twrp.img to make it easier to type.
Put it into a directory on your PC. Open terminal in that directory. Put the phone in fastboot, connect it to PC and execute the following command on PC terminal:
You will boot into TWRP. Then flash OOS-10, flash 3.5.2 installer, factory reset and reboot into system (if you can't do factory reset, just reboot in TWRP and repeat factory reset and boot into system. Then back to TWRP anf flash OOS-10 again followed by 3.5.2 TWRP installer. Boot into system. Now, you are ready to flash Jaguar.
Boot in twrp and flash Jaguar; then immediately flash TWRP installer (3.5.2). If you want Gapps, they must be flashed before the first boot into system. So, reboot in TWRP and flash Gapps and Magisk (optional). Then do a factory reset, where you get a prompt for 'yes' to confirm, and finally, boot Jaguar.
P.S. This is all done on unlocked bootloader. If you want to have Jaguar on locked bootloader, send me a PM.