Don't know. You can try these tips, they may or may not work.
View attachment 1625754
And check the answer marked as best on this thread, also may or may not work
I've seen people flash the same build twice and some of them got L1 back... worth a try I guess
Not working for One plus 7T
After Android 17 update?
[AMA] Join the OnePlus Nord CE 5G & OnePlus TV U1S Edition – Ask Me Anything
by Leo X., 2021-06-10