Oh my God! “I would say 99% likely …” You and I have also talked about this …
Status precisely proven by me here (S9) and here (S9+) as of 01/25/2021 as well as today and now:
The /e/asy installer 100% cannot update a Galaxy S9 / S9+ with /e/OS e-0.13-o-202012* aka Oreo-8.1 to /e/OS 'Q' aka Android 10.
If you don’t believe it, ask an /e/ official like /e/ communications leader.