Hi, thank you! I ended up trying bluetoothctl yesterday and it asked for PIN so I was able to pair it (I see the device even in the plugin). Now, despite being connected, I’m not getting any sound from the speaker 
so now I’m in the process of solving this.
Interesting info about PIN obsolescence, I didn’t know that. But still every now and then I get a request for “0000”, “1234” and these are definitely newer devices than 2.1 so probably there are devices which don’t respect or support SSP.