Permanently set app on launch (kiosk?)

I rooted my old Galaxy J2 today and replaced stock fw with LineageOS. Works great. My next quest would be to set Retroarch the first and only app on start up, which supposedly is kiosk mode,so as if the phone would basicly run Retroarch as its own system. I researched a lot about this (it’s how I know it’s called kiosk) but no clue on how to do this