[Nexus 9 Android Development] retiredtab:
You must read the FAQ before posting questions.

FAQ

Q1) Does the build work on Nexus 9 LTE?

A1) I have no idea. I only have the Nexus 9 wifi so I don't know if it will work on LTE. If you try the wifi build on the LTE, you may end up with a bricked device. Questions regarding LTE will go unanswered.

Q2) Application xyz doesnt' work. Can you fix it?

A2) I only fix what I use. If you use app xyz and it doesn't work, then go back to the last rom that worked for you. In addition, some of the code is not open source and in proprietary blob format so it's not possible to make changes.

Q3) My tablet hangs or crashes. This build is slow and buggy. Can you fix it?

A3) Go back to the last working stable rom for you. Some of the code is not open source and in proprietary blob format so it's not possible to make changes.

Q4) Do you plan to update the rom?

A4) Yes as long as I have high speed Internet, I wil try to release the rom monthly to incorporate the security patches.

Q5) What TWRP should I use?

A6) You must use 3.5.0_9-0 from

https://dl.twrp.me/flounder/

Q6) What is the difference between this rom and variants?

A6) Use whatever fits your needs. This is a stock LineageOS build with no modifications. I only offer this as an option for those who want or need a new rom and can't build it themselves.

Q7) Will there be a 17.1, 18.1, 19.1 or 20 build?

A7) Do not ask for higher versions. I'm an unpaid volunteer building this on my own time. Any questions regarding ETAs will go unanswered. If you want a newer version, then you can build it yourself.

Q8) Should I upgrade from stock or 14.1/15.1 to 16.0?

A8) It's entirely up to you. If you do upgrade, you will need to backup your data, wipe dalvik/art cache, system, data and internal storage in TWRP. You must also format data in TWRP. You cannot dirty flash from stock or 14.1/15.1 to 16.0, it must be a completely clean fresh install.

Q9) Can I build this rom myself? Where can I find the source and/or kernel source code?

A9) This is one of the few roms where it required no edits or changes to make it work. Follow the instructions at

https://wiki.lineageos.org/devices/flounder/build

The device tree is at

https://github.com/retiredtab/android_device_htc_flounder

The kernel tree is at

https://github.com/linckandrea/android_kernel_htc_flounder/tree/lineage-16.0

The vendor tree is at

https://github.com/TheMuppets/proprietary_vendor_htc/tree/lineage-16.0

Here's the manifest.xml

<?xml version="1.0" encoding="UTF-8"?>
<manifest>
<project name="retiredtab/android_device_htc_flounder" path="device/htc/flounder" remote="github" revision="lineage-16.0_update" />
<project name="linckandrea/android_kernel_htc_flounder" path="kernel/htc/flounder" remote="github" revision="lineage-16.0" />
<project name="TheMuppets/proprietary_vendor_htc" path="vendor/htc" remote="github" revision="lineage-16.0" />
</manifest>

You will also need to download the remove-liboemcrypto.diff if you're building from source because I couldn't get Disney+ to work with liboemcrypto.so. If you are NOT building from source, you don't need this patch file as it's already included in the 16.0 code.

To apply this patch,

# cd into your code directory
# now cd into vendor
cd vendor/htc
# apply the patch
patch -p1 < ~/remove-liboemcrypto.diff
# that will remove the command to copy liboemcrypto.so to the final rom build

If you are building from source, then you need to apply the monthly security patches as shown below. Otherwise, the security patches are already built into the rom.

# sync everything
repo sync
# now get all the 16.0 security patches that were not merged into LineageOS gerrit starting with
repopick -t P_asb_2022-05
repopick -t P_asb_2022-06
repopick -t P_asb_2022-07
repopick -t P_asb_2022-08
repopick -t P_asb_2022-09
repopick -t P_asb_2022-10
repopick -t P_asb_2022-11
repopick -t P_asb_2022-12
repopick -t P_asb_2023-01
repopick -t P_asb_2023-02
# and so on until you reach the current month

Q10) Why is my question not answered?

A10) It's likely because it's in the FAQ or it's off topic or you are asking something that I cannot answer for the reasons stated in this FAQ.

Q11) How is this 16.0 build different from the ones already on XDA?

A11) I modified linckandrea's code to meet my needs mainly for playing Clash Royale without lag. Without my modifications, the game would lag/slowdown after 15 minutes. With my modifications, I can play 30 minutes or more without lag.

Q12) Is the video hardware accelerated in 16.0?

A12) No. Hardware composer is broken in 16.0 and the GPU is used to do all the graphics.

Q13) Is encryption enabled by default?

A13) Some people say the Nexus 9 lags over time and supposedly removing encryption improves performance. The Nexus 9 is not a daily driver for me so I don't know, but reading the older 14.1 and 15.1 threads, I decided to change the default behavior so that encryption is disabled by default.

If you want encryption enabled, goto settings, security and privacy, encryption and credentials, encrypt tablet and follow instructions.

Q14) Can you build a variant like slimrom, crDroid, etc?

A14) No, but you can following the instructions and source code above that has been provided.

Q15) What gapps should I use?

A15) I use Aurora Store and have no idea what gapps works. You MUST DO YOUR OWN HOMEWORK in picking gapps. If you must use gapps, pick the smallest one to get best performance.

Q16) Where can I download this rom?

A16) See

https://sourceforge.net/projects/retiredtab/files/Nexus 9/16.0/