I have never used a keyboard to emulate a controller so I do not have hands on experience with this. However, you can read through
https://fs-uae.net/docs/keyboard I am not in front of my computer right now so I cannot check FS-UAE settings but I am pretty sure there is a way to remap keys.
Also, if SWOS is your biggest interest in Amiga scene, check out the unofficial PC port of SWOS 2020 @
https://www.sensiblesoccer.de/swos-2020 It is a native PC game with updated rosters, gfx (including shader & widescreen support).