Ah. For all that are coming back to SBricks after a few years of absence:
I didn't realize:
* the old firmware only has the LED blink once and then nothing
* iOS will not show SBricks in the list of Bluetooth devices (makes sense I guess since it does not offer any services interesting to iOS)
I was confused by:
* The app. The startup screen invited me to make a creation, and had me setup profile (I used Gamepad II 3.4) . That profile asked me to setup Channel settings but selecting that using the "Test" button hung the app.
If you want to see if your device works, it's better to choose the "SBricks" Option to list your devices.
It found my device (yeah!) and it offered a firmware upgrade. Now I have a LED that is always on and the profile works as well.
The LEGO battery block shows green light and runs motors when they are attached but the Sbrick does not seem to work.
I can see the LED shortly flashing when connecting the cable, but after that nothing.
Anything I can do?
PS
I bought and played around with the Sbrick around 5 years ago and just dusted it off but it seems dead. When reading this https://social.sbrick.com/forums/topic/8011/low-voltage-alert it seems to me that I am not the only one that has problems with older units.