Please add your suggestions to improve the documentation for the OnePlus - 5T - dumpling here …
Having installed /e/OS on two OnePlus5T devices and performed an upgrade from Oreo to Pie version on one of them, I researched posts on the community site here and noticed a number of people having difficulties with what should be a relatively easy install for those with some experience of flashing custom ROMs. As I have been using the Pie version of /e/ on my device for nearly two weeks now and been entirely satisfied with the way it works - save one important issue of backing up the system - I offer this round-up of various posts in the hope that it might simplify life for others thinking of installing /e/ on a OP5T.
Point 1 - Updates on the /e/ OnePlus documentation
The first difficulty I noticed while seeking information here on the official installation instructions was that references and links on the page were out of date. First of all the build from Lineage OS for dumpling is now at version 17.1 and they have their own corresponding recovery to flash it with. While this is not strictly relevant to an /e/ OS install, the firmware updates that Lineage also advises are now up to version 10.0.1 available here on their Sourceforge site.
The other link to download the TWRP recovery file is dead (posting a 404 error) and while there is mention in the “troubleshooting tips” at the end of the documentation page of advice to use a previous TWRP version “below 3.4.x.x” there is no indication of where to find it. My satisfactory experience after failing with the latest TWRP for dumpling was with the codeworkx 3.3.1 version available here. It was no problem to re-flash this version using ADB-platform-tools over the higher one, which solved the “error 7” failure. There are other versions of TWRP by mauronofrio and others which seem to work according to user reports on the xda-developers site, but not having tried them I can’t vouch for this solution.
Point 2 - clear installation instructions
While the instructions on the e.documentation page here and on the equivalent Lineage site are essentially the same with a few extra details by e-developers (one precision overlooked is the mention of the serial number followed by “fastboot” when the command fastboot devices is issued to be sure the phone is properly identified), I would advise any beginner to follow the excellent step-by-step explanation by @manish for the cheeseburger install. While this is for the OnePlus5, his screenshots are easy to follow and you only need to change the links given here for the custom recovery and the /e/OS files to use it for the OP5T.
Point 3 - other problems encountered
Another problem sometimes mentioned after a first flash of a TWRP recovery is the fact that rebooting into the stock system (without having installed a custom ROM) immediately afterwards replaces TWRP with the stock recovery. So instead boot into recovery with the phone (using the hardware buttons) OR use fastboot boot twrp-xxx.img to boot into the recovery image. Worse can happen if you try flashing a new TWRP image immediately after unlocking the bootloader on a recent Pie version of OxgenOS. I have read about bootloop problems but perhaps someone can complete this information.
Additionally, posts by @Carlos & others seem to show that a re-loaded stock recovery can block a sideload installation of the /e/ zip file as he discovered when he realised he wasn’t using the TWRP recovery.
@mousersmb2 also had the problem of getting the right TWRP recovery installed and then the warning message after flashing the /e/ ROM that there was “No OS installed”. This seems to be an error that can be ignored.
Further information on unlocking & flashing TWRP
This page by Funk Wizard on the xda-developer site (although 3 years old now) also gives clear step-by-step instructions using screenshots, as well as rooting the OP5T but obviously has no information concerning the /e/OS.
Here is a more recent guide to installing TWRP and rooting a OP5T with an OxygenOS updated to Android 9 ‘Pie’. It has useful links to the other TWRP versions I have mentioned and advice on setting up the device using adb on a Windows PC.
Upgrading to Android 10 'Q’
@itsclarence has built a successful “unofficial” version of /e/ on the more recent Android Q system, but perhaps users who have managed this installation could let us know if an upgrade can be done via a complete factory reset or if it’s necessary to go back to a stock OxygenOS before sideloading this newest version of /e/. From user comments it sounds like an upgrade we can look forward to.
My apologies for this long post, but I hope it might be useful to anyone thinking of installing /e/ on what is still IMHO a very good phone, in spite of its age (3 years old).
The updates to the documentation to get it in sync with the 17.0 or Q changes, were checked in a month back but have as yet not been published. I am checking with the team that handles the publishing to speed this up.