As also others stated, the best option is a SCSI scanner (cheap on eBay and similars).
If you don't have an accelerator board with SCSI option, get a Squirrel or Surf Squirrel to connect your scanner to the PCMCIA port.
I used an Epson GT-5500 10 years ago.
ScanQuix is the best software on Amiga, I think, but it's commercial.
But on Aminet there is some free software as well: check out which scanners this software (eg. Betascan) supports.
BY!