UPDATE
H2os rom update 19th may 2018
Changelog
1) Heat fix,may result in more battery life.
2) performance optimisations,
3) Added oss cam hals,
4)localised for india.
5) Radio updated,resulting in more stable network receptions.
6) Rom is stable af.
7) Fixed Charging issues.
8) Fixed Magisk root failures.
9) other optimisation and fixes.
FLASHING INSTRUCTIONS
1) Flash Rom zip,reboot
2) Setup your google account, use google installer to install gapps,
3) flash afterflash zip, don't flash it before setting up google account as this will make account setup crash.reboot.
4) Flash Magisk if u want root, reboot.
5) let the device cool after flashing.
6) additionally you can flash any thermal mods, sound and other mods too.
Note:
1) If you have play store crash, see point #3 above, if its fine then clean data of play store and play services. If still doesn't work then let it download latest play store, it will update automatically.
2) If you have contact sync issues, download contact app from google, if you have trued many other tricks and contacts are still not syncing then let rom take its time, it will sync automatically after few hours.
3) portrait mode in gcam is still buggy, you can install other apks too.
Edit:
Forgotten to mention in changelog post.
Added support for custom kernel,some of them cam improves volume output too along with performance nd battery,
Though its still in beta,its pretty much stable.
if u r flashing custom kernels, it means you are TESTING this feature.
i m expecting Bug reports rather than complaints.
I Dont have enough time to test every ro for couple of days, i have tested following kernels for few hours , almost every compatible(non treble,nougat) kernels are booting and stable too.
ArBeast R6 - N
Heliox-N
Heliox N with wlan as module,
Uberkernel
DarkMoon Kernel
Jaguar N Kernel.
If a Kernel is Causing Unexpected results , be patient as i have noticed some of these kernel takes some times to settle(jaguar took 3 4 hours before full stable).
if u want to restore stock kernel, flash rom zip again, setup google account and then flash afterflash zip.
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H2OS 31/03/2018
1) OSS Cam Hals Are Fully Supported Now,Gcam With Portrait Mode Works without FC.
2) Fixed Charging Issue.
3) Removed SuperSu.
4)Added Swifkey(Dev Forgot to Include Keyboard)
5) Added H2os AfterFlash.zip which
-1) Enables Oss cam hals ,Apply cameraFix from Youlinw.
-2) Creates Folder 'H2OS ExtraFiles' which contains
-- 1) Magisk v16.0
--2) Pixel Mod camera by Arnova (gcam) and MGC cam
--3) Futuristic Pixel launcher
--4) Some Magisk modules which may improve ram performance and may enable Slow motion in Gcam.
--5) Google Installer 3.0 apk,Gboard Apk in case Swiftkey Fails.
--6) Universal SafetyNet Fix And Other Magisk Modules.
Flashing/Setup/installation Instructions
This Rom don't support encryption, so if u r coming from ZUI, erase your data, only official TWRP is supported, no need to unmount system or anything, you can flash in normal way.
1) Flash Rom zip=AfterFlash zip.
2) Skip setup, Go to Setting/Languages & Input/Virtual Keyboard/enable swiftkey there.
3) Go to File manager then Storage/H2os ExtraFiles Install Google Installer apk,setup But Dont Login.
4) Go to Setting/Apps/ Give Permission To all Contact/Google Apps In order to solve Sync Issues,Then Login In Play Store,Reboot.
5) Install PixelMod camera Apk From H2OS ExtraFiles Folder,
6) There Are More Files/Apks You can Install them if you Need them
Tips And Tricks/Known Issues/WorkArounds
1) To Solve Yellow Tint on Display/Screen See Atachement.
2) If Portrait Mode Crashes,First Switch To Front Cam Then Enable Portrait Mode,If Its Crashing Too Often,Try other Provided Apk
3) If HDR+ Doesn't Work, It will Work With Portrait Mode, As Portrait Mode Only Works on Humans,If Will Apply Only HDR+ Instead Of Portrait Mode Effect,Other
Provided camera Have Working HDR+ , But Portrait Mode May Crash More Often,Though You Can Use Both Or One Which Suits You Better.
4) For Contact Sync Give All Permissions To Gapps.
5) If Third Party Camera Apps Not Working , Reflash AafterFlash Zip.
6) No Notification After Clearing Apps From Recent? Disable Aggressive Doze Under Battery Setting.
7) Low Volume?? Try any Sound Mods Like Shox/Dolby/Viper4A Or any Other of Your Choice.
Note: Though I have Tried My Best , Still There May Be Gcam Issue/Fc, Its Greatly Improved from Recent Build, But Portrait Mode May Crash Sometimes, For Me, Its Crashing 20% (Crashing 2 Times Out Of Attempts).
UPDATE
Update:AfterFlash2
Some people's reported that gcam is crashing for them.
I have updated AfterFlash zip with some more files, if its crashing too for you, flash the included magisk modules in AfterFlash2zip.
These modules should reduce gcam crashes, for me its crashing once out of 10 attempts (10% crashes)
Ready To Flash??
Here is download link
https://drive.google.com/drive/u/0/mobile/folders/1GuDm5c8XI9L3g_nXtCjS1j-14Mdy0gv5
Read Full Post Carefully Before Crying For Help.

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The original dev 'Youlinw' have updated h2os on 20 feb 2018,
I have found and easy workaround fir enabling cam 2api pixel camera with working portrait mode without force closes/crash, just need to flash two zip files which will patch boot.img and place camera related files in appropriate locations, so it won't break existing oneplus camera so there will be no conflict and gcam will not crash, as it was happening on last build.
This time, I am not updating rom, you just need to flash rom, then zip provided here.
|| Flashing instructions ||
1) wipe data, system, cache, dalvic cache (clean flash is always recommended)
2) flash the original rom
3) boot into rom, setup, disable Chinese bloatware and system apps which you don't need (don't disable baiduIME this is default keyboard)
4) install google installer, press blue circular button to install play store, once all apps are installed, login your google account, tweak the rom as you want.
5) the reboot to twrp,
Flash oss cam hal enabler v1. Zip
6)reboot,use the rom for few minutes, then
flash oss cam hal enabler v2. Zip
7)reboot, install camera apk given in link, then use default settinga, you can tweak if you want but that may or may not cause stability issues.
Enjoy!!