[OnePlus 9] op9journey:
Here's a few days of non stop research to solve your issue, pay close attention.

The LE2110(China) and LE2111(India) both run the India software version, so when people refer to India variant both those hardware devices are applicable. China was released with Color OS instead of Oxygen OS however it is essentially the same hardware as the India device so it behaves the same.

There are many ways wonderful to brick an OP9, in the India variant case it gets especially tricky to unbrick. Credit to https://droidwin.com/unbrick-oneplus-9-pro-msm-download-tool for trying to explain how to unbrick yet didn't make it too clear as all the variant names can get confusing and many of his links are dead.

"Moreover, you will have to first flash the unbrick firmware using the OnePlus 9 Pro Indian variant and then use the below-patched tool." In our case we want the India 9 Pro MSM to unbrick (seems to help unbrick all OP9 variants) but not the below patched tool since it isn't for the OP9 non-pro INDIA variant (LE2110/LE2111).

Sources for the OnePlus 9 PRO India variant LE2121 MSM tool (OnePlus_9_Pro_India_OxygenOS_11.2.4.4.zip or lemonadep_22_I.07_210412.zip):

https://onepluscommunityserver.com/list/Unbrick_Tools/OnePlus_9_Pro/India_LE15DA/R/

lemonadep_22_I.07_210412.zip | by craznazn for OnePlus 9 Pro

Download GApps, Roms, Kernels, Themes, Firmware, and more. Free file hosting for all Android developers.

www.androidfilehost.com

You will need to first flash this MSM package with settings Target India and Lite Firehose checked (worked for me). This is what got me out of all the other MSM errors I was getting trying all the different MSM packages out there.

After that succeeds and your phone is back alive you can run the "OnePlus 9 India MSM Download Tool - Oxygen OS 11.2.4.4.LE25DA" MSM package (lemonade_22_I.07_210412_repack_by_MlgmXyysd.zip) which I finally located here:

一加9/9008线刷救砖包氧OS 11.2.4.4/印度版 - 一加手机官方ROM - 一加手机官方ROM下载

本站提供一加全机型ROM下载，包括一加Ace 2V、ACE2、Ace/10R、一加10 Pro、9Pro、9RT、9R、8T、8 Pro、一加8、7T Pro、7T、7Pro等全系一加机型的升级全量包、降级包、9008线刷救砖包等各种官方和原厂ROM，全部资源完全免费，不限速，无需登录

yun.daxiaamu.com

And with this actual Oneplus 9 India LE2111 MSM restore tool you can get your phone back to stock. You will need to select target India again but this time NO "Lite Firehose" checkmark. That should successfully run without all the MSM errors now that you previously unbricked with the Oneplus 9 PRO MSM tool, assuming it didn't work before (worth trying directly with the non pro MSM first before the pro version).

MSM is a whole thing of it's own so good luck getting it properly configured. vol up + down + power while usb is attached is a good way to get it to pop up however in my case it kept connecting and disconnecting until i started the restore process. Sometimes you'll need to disconnect it and hold the power button a while to reset it from being frozen after trying different options in the MSM tool. Here's some help on that issue: https://droidwin.com/fix-sahara-communication-failed-error-msm-download-tool/

Once you restore OOS 11 you might find you can't update to OOS 12 with the built in system updater it will just say it failed after restarting (I tried many local images too and all failed, only downgrades worked). The last OOS 11 version is 10.10 so update to that one and then download the C.47 OOS 12 release onto the device itself and flash it using this version of twrp-3.7.0_11-0-lemonadep.img (what worked for me). You can temporarily boot TWRP using fastboot boot twrp-image-file.img. It will give some errors when installing but remarkably will get you to OOS 12 and from there you can update the software quite painfully release by release and eventually make it to OOS 14 (last step might require a loading a local image from here https://xdaforums.com/t/oneplus-9-rom-ota-oxygen-os-repo-of-oxygen-os-builds.4254579/ assuming OTA doesn't come through). There might be more direct ways to upgrade but this seems to be the easiest.

I did however find I could not relock the bootloader once making it to OOS 14 it would essentially fail with "The current image (boot/recovery) have been destroyed" when booting; therefore I recommend locking the bootloader at OOS 11 after MSM restore (worked for me), or if you need to use TWRP to get to OOS 12 try locking it right after you upgrade. If it fails then just unlock the bootloader again and assume you won't be able to lock it easily down the road.

Speaking of locked bootloaders, OP9 does not support custom avb keys past OOS 11 so if you want to lock the bootloader with custom roms stay on that version there are a few out there like the hardened JaguarOS. Not necessarily the safest staying on A11 but if bootlocker locking is important to you that's your only option.

Another point to take note of, I've noticed Lineage OS based roms have a serious Wifi issue which is that it's much slower than it should be (30Mbps instead of 220Mbps in my case). I've read disabling randomized MAC addresses helps, in my case it didn't. I've also read about router configuration fixes, but turns out it's just a software bug because after installing ParanoidAndroid 14 Uvite beta 3 everything was smooth and fast (they make a note in the changelog that they fixed wifi issues, could be related). Crdroid, nameless, lineage, and divest all had this wifi issue and playing around with the settings in these lineage roms didn't help either.

As for the unbricking, this guy also realized the same things I did, figured I should give him a bit of credit too :)

[ADVANCED] [UNTESTED] Possible Fix - MSM Errors (Sahara, Param info, etc)

WARNING: THE FOLLOWING IS FOR INFORMATIONAL PURPOSES ONLY AND MAY FURTHER DAMAGE YOUR DEVICE. EXERCISE EXTREME CAUTION. USE ONLY AS A LAST RESORT. This was tested with a Global OnePlus 9 LE2115 Overview So I was encountering an error with MSM...

xdaforums.com

Good luck on your journey.