@pierrel, that is anything but satisfactory.
Stock Android 10 on the S9 is already first class. However, CustomROMs like LineageOS (support now discontinued), iodè 10 and /e/ OS ‘Q’ Android 10 are the better choice for me. A return to /e/ OS 'O’reo is absolutely out of the question for me. That /e/ after all these weeks is still not able to let the /e/asy installer install a /e/OS ‘Q’ ROM is more than poor.
The same situation was with /e/ asy installer and Gigaset GS290 until a few days ago. The problem was fixed after weeks. Without me knowing, it can be assumed that the S9 /S9+ installation problem will also be fixed at some point. Until then, you must manage to upgrade your S9 to Stcok Android 10.
Only when a stock Android 10 is functional on your S9 will it be possible to install a CustomROM ‘10’ aka /e/ OS ‘Q’. For the sake of testing, I’m already running an experimental LineagsIS 18.1 (Android 11) and a GSI AOSP 11, which shows what’s possible and what we’ll still have a lot of fun with our S9 / S9+.
Still, it is the way it is - because the /e/ team doesn’t change anything. As a Windows and Odin user, I’ve not yet encountered your ERROR: Failed to send end session packet!, but brief research shows that this ERROR in connection with Heimdall goes back to the 2014 years.