As an expérimentation, is it possible that an advanced user, make this test :
Take a device running updated stock 11,
Flash a recovery if possible,
Change /vendor.IMG to an older, ( extracted from a stock 10 firmware )
Format /data, and Wipe /data /system /cache /davilk-cache,
Install /e/-0.17-Q
Thanks in advance.
That is what the easy installer seems to do for installing oreo.8 over stock android.10 on the Samsung s9/s9+