E-UAE is available for OS4 for old games.
Dunno how compatible it is since my A1 is up on the blocks at the
moment and I'm not that into gaming these days anyway.
AOS4 can run alongside Linux (same goes for MorphOS on the PagasosII,
which is another option you might consider - I'm typing this on a
PegI) but you can have OS4 installed on it's own. I have Debian
installed on my A1 but Ihaven't used (Debian) in many months.