Hi,
To go back to stock ROM, I strongly advise to use SP Flash Tool (Linux download here) with the scatter file, as described in the how-to.
I used this method 10+ times now (on a Windows computer), everytime it ended up with a fully working device.
I have to admit, I never took care of partitions list when going back to stock. Just clicked on the green button, plugged a powered-off phone, and voilà 
As AndroidFileHost is subject to frequent outages, I maintain a mirror for the version of stock ROM I use : Stock GS290 Rom anyone? - #20 by smu44.
I got it first from AndroidFileHost, when GS290 was quite new for /e/.
You’ll have to install 4 or 5 updates starting from this ROM, before flashing /e/.