8Bitdo SF30 Pro L2, R2 not working

[BloBlo]

Hello,

is there a way how to assign L2 and R2 buttons on controller to L and R buttons in PPSSPP? I am using Ubuntu 20.04 and SF30 Pro controllers. Currently I can use only L1 and R1 which are smaller and I'd like to swap them with L2/R2. The problem is that they are not recognised when I try to map them in PPSSPP. It is weird because they're selected by default. Anyway, if I press them it does nothing. I know that PSP does not have L2/R2, but it should be possible to assign whatever button to L/R. On SF30 Pro they're simply ignored. I can use keyboard and map whatever key, but not with the controller.

What can I do?

Thank you in advance.