New build called lineage-15.1-20220128-UNOFFICIAL-flounder.zip
Jan 28, 2022 release notes
1. Incorporates Jan 5 security patches as per
https://review.lineageos.org/q/topic:O_asb_2022-01
2. Whatever LineageOS changed since Dec 2021 (about 1,200 files had to be recompiled).
3. I completely resynced back to stock LineageOS so the security patch will show Oct 5, 2021 as that was the last official Android 8 patches from Google.
4. The security patch string will permanently stay at Oct 5, 2021 as per Kevin's message at
https://review.lineageos.org/c/LineageOS/android_build/+/320334
"lineage-15.1 is officially discontinued, so this is as good as an official announcement.
That aside, it is irresponsible to bump a patch level when there is no more assessment being performed by the group that defines the patch levels. It's entirely possible, certain even, that there are vulnerabilities in <= A8.1 that are reported and unfixed in A8.1 that would be documented in an ASB if Google still maintained the branch. Bottom line, there is no such thing as a set of changes to A8.1 that make up anything beyond 2021-10-05. Bumping the patch level should never have been done in the past on any other branches."
5. So despite what the security string says, this Jan 28th build includes the unofficial Google Nov and Dec 2021 patches in addition to the Jan 5th 2022 patches.
6. I recommend that you wipe cache/dalvik AND cache in TWRP after you flash new build. Supposedly, the Nexus 9 internal flash file system gets slower over time and that wiping the flash and keeping as much free space available helps avoid the slowdown.
7. During first boot, the Google white logo may display up to 3 minutes. DO NOT PANIC. It will eventually start LineageOS boot animation and the build WILL load (I test ALL my builds to make sure they boot and work as post #1).
8. With the Jan 28, 2022 build, I have no problems playing Clash Royale for 30 minutes straight as there's no lag or freezing.
9. For those upgrading from my 15.1 2021 builds, there may be a problem after flashing the 2022 builds with respect to screen password, pattern or pin unlock. Three people have reported that the screen unlock doesn't work when doing the above (i.e. from the Dec 5. 2021 to Jan 5, 2022 security patches).
If you have screen lock enabled, I recommend you remove it first from the current running OS, then boot into TWRP, do the upgrade and then put the screen lock back on after it boots.