(funny, kind of) Today on a different computer, my own instructions did not succeed.
Debian-12, Python3.10.15 from conda, prereq as above, everything installed by just pip, building very long for the wheels. Psychopy is version 2024.2.1
But then, same behaviour as @kbmcgowan 's initial description, no builder-, coder-, runner-windows open.
Solution (following a hint from Jon for Mac here : kill the hourglass with Ctrl-C, change lastFrame to “coder” in ~/.psychopy3/appData.cfg (deleting the tree did not help). Then psychopy did show the coder window, and switching windows worked.