It appears that the correct sequence of installation steps has not been followed. This is why WinTeam TWRP Recovery was not installed.
It is very important to restart immediately after installing the custom recovery.
6.) Now reboot into recovery to verify the installationd
Otherwise, the WinTeam TWRP Recovery will be overwritten by StockROm Recovery and the device will be restarted.
ADB Sideload only works properly with TWRP Recovery.
TWRP is installed but fails to start the ADB Sideload process. Any advice?
Do I have to start ADB Sideload only on the device or also on the Notebook?
ADB Sideload must be operated on both devices …
Ok, understood…
When I start ADB Sideload on the Notebook I get an error message:
[scheff@scheff-pc ~]$ sudo adb sideload e-0.7-n-202221541379-dev-s2.zip
[sudo] Passwort für scheff:
adb: failed to stat file e-0.7-n-202221541379-dev-s2.zip: No such file or directory
Another advice avalable?
As for TWRP, you must provide full path for the zip file 
If the files to be transferred aren’t in the same /directory aka /path of ADB & Fastboot tool, additional /path information must be given so that they are transferred from ADB & Fastboot Tool.
/e/ documentation
Install /e/ on a LeEco Le 2 - “s2”
Installing /e/ from custom recovery
8.) Sideload the /e/ (e-0.7-n-*).zip package:
8.1) On the device (LeEco Le 2 X527), select “Advanced”, “ADB Sideload”, then swipe to begin sideload.
On the host machine (Arch Linux Notebook), sideload the package using:
8.2) $ adb sideload /**path**/**to**/e-0.7-n-202221541379-dev-s2.zip
https://ecloud.global/s/jgCBFPGDE96x8w5
9.) Once installation has finished, return to th WinTeam TWRP main menu, tap Reboot, and then System (see also images posting #27)
Hm, still not sure “where to go”…
I have a folder “Android” that contains a folder “Sdk” and that contains nine more folders named “build-tools”, “emulator”, “patcher”, “platforms”, “platform-tools”, “skins”, “sources”, “system-images” and “tools”.
I copied the files from the folder “platform-tools” into the folder “home” so the path would be
$ adb sideload /home/scheff/e-0.7-n-20222154379-dev-s2-zip
Error, “no such file or directory”…
So then I copied the /e Image into the folder “platform-tools” and changed the path to
$ adb sideload /home/scheff/Android/Sdk/platform-tools/e-0.7-n20222154379-dev-s2-zip
Error, “no such file or Directory”…
Any more suggestions?
Yes, the file is not there. So be sure you have the correct path:
find -iname e-0.7-n-20222154379-dev-s2-zip 2>/dev/null
Now the full path must return otherwise the file is not there or you have the wrong filename.
If the full path is found, use that in your sideload command.
Hi andrelam!
I followed your advice and got a “empty” answer:
[scheff@scheff-pc ~]$ find -iname e-0.7-n-20222154379-dev-s2-zip 2>/dev/null
[scheff@scheff-pc ~]$
But I did download the /e image? The file is definitely in the /home directory and I did not change its name…
WHOA, wait a minute!!!
When I follow the link to the Download from the install instruction page the image is named
e-0.7-n-2020021541379-dev-s2.zip
Where do you get your file (e-0.7-n-20222…) from?!
Installation alternative WinTeam TWRP
Download the file → e-0.7-n-2020021541379-dev-s2.zip with your Arch Linux Notebook
Boot into TWRP Recovery
Copy the file → e-0.7-n-2020021541379-dev-s2.zip into the Internal Storage of the LeEco Le 2 X527.
Now tap “Install” and select the file 0.7-n-20222154379-dev-s2-zip from the Internal Storage
If TWRP message … done … tap “Dalvik / Art Cache” swiping appears and the system is rebooted and initialized.
That should be it then!
Download /e/ for s2 * dev (nougat)
Hi archje,
where is the file e-0.7-n-20222154379-dev-s2-zip from? It’s not from the Download page…
I copied the name from your own post 
OOOPS
Shame on me… 
Just find the correct filename and everything should be file.
Could you please change the post headline with [SOLVED]
Thank you.
TADAAAHHH!!!
Now I’m after a lot of time, blood, sweat, tears and curses an official user of the /e custom ROM!!!
I apologize for the many stupid and stubborn questions to the community and thank you all for your patience and support!
You’re the best team around!!! 
Could you please change the post headline with [SOLVED]
How do I do this?
Go to the top of your post. In the title bar, on the far right is a icon “Pencil”. This simplifies “edit”.
Now you can insert the word [SOLVED] at the beginning of the title bar.
Finally, click the blue button [ ✓ ] on the very left. That’s it.