This is an SM GT900F.
I tried to install TWRP per these instructions. However, when issuing
heimdall flash --RECOVERY recovery.img --no-reboot
I got this (some clutter removed):
Initialising connection...
Detecting device...
Claiming interface...
Setting up interface...
Initialising protocol...
Protocol initialisation successful.
Beginning session...
Downloading device's PIT file...
ERROR: Failed to send request to end PIT file transfer!
ERROR: Failed to download PIT file!
Ending session...
ERROR: Failed to send end session packet!
Releasing device interface...
The phone was then stuck with a tiny blue dot on the left, which I suppose is the start of the blue progress bar mentioned here. It wouldn't react to anything anymore.
Fortunately, after removing the batteries, it boots just fine into the stock ROM. (Phew.) I have repeated this twice since, but this is consistent.
Does anyone have any idea how I should proceed?