They are bound to apps, except for one blank button “for all apps” as per here (Make Stream Deck to blank when changing apps - #2 by Andreas_Hegenberg).
The weird thing is that this issue only occurs with the BTT software and the SD Mini. All other combinations using the SD software and a SD Neo work fine. Even when I try having the SD Mini plugged in simultaneously with the SD Neo, the Mini doesn’t light up but the Neo works perfectly.
I’ll send the logs later tonight.