[OnePlus 5T  ROMs, Kernels, Recoveries, & Other Dev] mad-murdock:
Man, living the dream, having something new to flash every day or every second day... Stuff getting better and better... Custom ROMs at their best..

20181213 is the bomb. Smooth as my freshly shaved a.... Skin

--------

OMNI 9 interims install guide #notadev

Hi, I am the Install-Guide Guy. I did it multiple times and I do it again. If I got something wrong, just tell me, and I probably will update this guide. If someone asks how to install this ROM - and the OP is not enough for that person, you may point him/her here if it fits. Or just answer their question.

Precautions

This guide assumes, you know how to flash and access recovery, and even have flashed a ROM sometime before in your life. You just want to try THIS ROM and dont know what the eff is going on with this new shiet. If you are new to flashing overall, there are a ton of good guides at other places of this forum.

NSA-proof encryption

It cannot hurt to remove the lock-code of your current (old?) ROM and switch it to slide-only-unlock before continuing.

The vendor situation

This ROM uses the vendor image of official OOS. Its nice, since ROM .zip files are keept short, we have full compliance and its easy. You only have to flash vendor once and maybe update once a new OOS version is released.

You are free to flash vendor image before, after or multiple times if you feel like it. But once is enough. Just be sure, if coming from Oreo, that you once flashed any firmware version 5.1.5 or above. Without, there is no actual vendor partition, without you cannot flash the vendor image and yeah, it wont work :)

If in doubt, just flash firmware from OP first, then reboot to recovery and you have a vendor partition now.

Recovering

While all newer recovery versions floating around I saw support vendor, only the latest blu_spark recovery (latest meaning its from september) does offer user-facing vendor support. Meaning that all those recoveries offer /vendor partition to .zip-install-scripts, but you have no vendor in the mount-menu or you cannot flash vendor yourself just with the UI. This bluspark build does offer this feature.

Recovering the vendor (from harm?)

UPDATE: Latest OP Vendor "OP5T_pie_ob20_fw_and_vendor.zip" contains FW as well. Will update soon. For now, just flash this as you would usually flash vendor. ;)

In mentioned TWRP, go to install, then press the "from zip" button so it switched to "from image" and select the vendor image from OP. After selecting you have the choice to go "boot", "system", "vendor" and more, just choose "vendor" here, too. Make sure to have "reboot after flashing" disabled so you can do more work when done. Flashing images goes really really fast. Once its done, switch back to "from zip"

The usual

Thats basically it. From here it is, what you are used to. Namely:

Wipe system. If in doubt, go to advanced wipe and select "system", "cache", "data", so no backups of your old - i.e. gapps - will be backed up and restored. You can also select vendor and flash it again, but it is not needed since you just raw-wrote it.

Flash firmware from OP and latest ROM. In any order. Firmware only needs to be flashed once. ROM flashed every so often, when you feel like it and there is a new version out there. If you switch between ROMs, make sure to always flash the right firmware for the selected ROM. In our case - for now - it is linked in OP. Might change any time, then just ask here.

Flash gapps. People had trouble with bootloops if going for brandnew gapps. Might be fixed (probably on gapps side) already. If not, use september gapps. Mine are 20180926-arm64-nano ... For now you get them from the official gapps page. On their github there are links to old versions. For later I probably link them here. If latest gapps work, also let me know.

If you want to flash magisk, let the system boot once after gapps. Once its booted, reboot to recovery and flash magisk as you like. 18.0 is the latest dangest thingie at the time of writing.

Thats basically it. Welcome to a good, real-oos-vendor-based, not-cm-but-aosp-based, battery friendly and smooth ROM.

AWMYGAD, I did as you said, my phone wont boot

Well, friendo, let me break the news. Its not really good news, but apart from being time intensive, its also not bad news.

You know, devices are encrypted, and in the early days of device encryption HOW they were encrypted was different in different ROMs. Even worse, it was different in different versions of ROMs. To me, it seems like this is kind of stuff of the past, since nowadays you dont have to format your phone when forgetting to remove the encryption key when installing new stuff, but hey, what do I know what ROM you are coming from.

If you phone wont boot, what you have to do is format the WHOLE data partition. Yes, you lose everything, thats why I tell you the fastest way to backup and restore below, but for now lets assume you have nothing important on your phone.

In TWRP you just go to wipe -> advanced -> internal storage. This should do the trick. A more nerd-friendly way is

fastboot format userdata

Both methods remove all encryption and all data - including "sdcard" - from your phone. Once you did this, you can boot again, and I bet your phone will boot you to your first-time-setup this time. Sorry bro, this is the price we have to pay for evolving encryption. I would not suggest to go unencrypted for different reasons I will not discuss here. The only hint: You are unlocked already. It is not wise to be unlocked AND unencrypted. Also encryption has zero impact on performance or battery on your device.

Backup&Restore

If you have to backup for above formating, the fastest way I know of, even beating "adb shell tar xfz - | tar cz" (if you dont get that, dont worry, its not important) is... *drummroll*

Backup

cd emtpy-directory
adb pull /sdcard

Restore

cd now-not-empty-anymore-directory
adb push . /sdcard

It will backup/restore all your "sdcard". So if you did a backup with TWRP before, it will also backup the backup. All pictures and whatsapp should be inside. Not included are all apps and settings and contacts and calendar. Should be cloud-saved anyways. If you got no clue what I am talking about, ask here before doing this big step.

TL;DR

There is no TL;DR. Well, there is one, but it is in the OP. If the OP was not enough for you, then you needed this. I love a "thanks", but don't feel obliged to.