Ok, there is no “install” option on this recovery (unlike in TWRP), so maybe should I go back to “Download mode”, and push the new recovery through? But in that case if I understood well it’s not persistent and it shoud be immediately booted in Recovery mode…
How to do this on my S9? (I can only boot in standard mode with VOL DOWN+POWER, other options does not work)
The heimdall test (print-pit) + flash command (progress bar + messages) was OK, so I tried with a TRWP img (to doucle check with a different img), and without the " “–no-reboot” option, and when the device reboots it does not boot in the recovery mode (means the uploaded img is then lost)
And I finally found the correct procedure.
Shut Down the phone, disconnect the USB cable
Go in download mode (“Bixby key” + “Vol. Down” + “Power”)
Plug the USB cable, then “Vol. Up” button to continue
Execute the flash, with “heimdall flash --RECOVERY image.img --no-reboot” (–no-reboot is important to have more time for next steps, but I guess you can do without).
Wait for the progress bar to complete (and heimdall to exit)
Disconnect the USB cable
Press simultaneously the “Bixby key” + “Vol. Down” + “Power” (instead of only “Vol. Down” + “Power” as described on the phone)
The tricky part : at the precise moment the screen becomes black, immediately release the “Vol.Down” button and press the “Bixby key” + “Vol. UP” + “Power” buttons during 10 to 15 sec to enter the recovery mode
If it didn`t worked, redo the steps from 1. more careful this time.
Believe me or not, but I tried and tried again. It perfectly worked when I flashed with heimdall from my stock S9 to /e/ recovery, removing the “–no-reboot” made the device reboot in recovery mode… (and with /e/ recovery it booted only on os if auto-reboot)
I may have a clue… While cleaning up some recovery images from my drive, I just realize that the /e/ recovery I was using (and flashed OK) while having this issue was a star2lte recovery (S9+) and not starlte.img (S9) : could it have created this behavior?