Were you asked to press a continue button (was it off you screen ? can happen on a wide screen laptop!)
Or … there are a few preparatory screens to walk you though some things you have to do first. You might concentrate on those to see if anything was missed.
Many thanks, aibd, for your reply. I tried again and am now getting stuck at a much later point: After going to much of the Easy-Installer process, the Samsung Galaxy S9+ shows a blue screen saying “Downloading…” (attaching a photo doesn’t seem to work right now; I’ll try again later). The logfile can be downloaded here: https://paste.tchncs.de/upload/fish-pigeon-lizard
For the moment, I’m still hoping the installation process will continue, so I’m leaving the device connected. But I’ll have to deconnect it at some point and try the whole process again - only I don’t quite know what to do differently… Many thanks for any further help!
Any Google account must be removed. Often we find that the device needs to be online to lift some mysterious lock, please watch for that lock indicator to change if you get the phone online.
Edit Is the phone new?
The phone may be protected against a Custom ROM if you have not used it “normally” for a minimum of a week or two.
You might attempt “Check for Updates” within the existing Samsung UI. If remote monitoring applies this forces a connection.
Many thanks for these very helpful additional hints! I now got to the blue Downloading… screen. How long should I wait before I restart in recovery mode (pressing “on”, “Bixby” and “volume down” at the same time)?
Thank you very much for these additional pieces of information - I now managed to complete the installation, using the very helpful explanation you shared concerning the button presses. I’m very happy it worked!