8BitDo Pro 2 connect

How to connect such joysticks via bluetooth?

I set the switch to D on all controllers
Then I connected two, but after a reboot, EmuElec does not see the second joystick.
I have to re-configure them, but this is before the first reboot

Are you using EmuELEC version 4.6? 4.6 has a buggy Bluez version which does not work with as many controllers as EE 4.5, so you might have to downgrade to get them fully working.