Comment by MagerValp

If you want to run demos, you need a device with (close to) 100% 1541 compatibility. The Ultimate II+ cartridge is your best bet, but it’s a bit pricey and availability is sometimes spotty. Pi1541 is a cheaper option, especially if you diy, but you’ll need a fast loader solution as well. KFF, sd2iec, and other cheap devices don’t offer hw level 1541 compatibility and can’t run demos.