I find Lionheart plays much better with a control pad (using 2 buttons) than with a joystick. I use control pads on most of my Amigas, although I prefer to play some games with a Joystick, like Shadow of the Beast and a few others that need you to press up to jump.
An A4000 keyboard will plug in without an adapter, and an A2000 or A3000 keyboard will fit with a simple AT-PS/2 adapter, but make sure it's a corded one and not the short, fat plug type, which can pry the AUX port connector from your motherboard if they're knocked around too much, which will blow your capacitors and stop your CD ROM drive from reading. This is the right one to buy -
http://amigakit.leamancomputing.com/catalog/product_info.php?cPath=49&products_id=230You can also use a Lyra Keyboard adapter which lets you use a PC PS/2 keyboard on your Amiga and CD32. You can get these here -
http://www.redsretro.com/index.php?main_page=product_info&cPath=1&products_id=18 or
http://www.vesalia.de/e_lyra[1115].htm or
http://amigakit.leamancomputing.com/catalog/product_info.php?cPath=49&products_id=228You won't be able to use a keyboard as a replacement for a control pad or joystick though, unless the individual games have the option for keyboard control.
You can also get a Boomerang CD32 pad, which is the only other aftermarket CD32 pad anyone made apart from the Honey Bee/Competition Pro. They aren't very good, to be honest. They're okay when you plug the thumbstick into them, and the three face buttons are big enough, but the other buttons are hard to access and everything has a clunky feel to it.
You might be happy to know that we are currently working on producing a batch of Playstation-to-CD32 adapters which will allow you to use virtually any PS1/PS2 controller as an Amiga controller, using all the buttons and providing extra features like remappable buttons (useful for remapping UP for jump to a button), analogue stick mouse control, auto fire and more. We're also working on a simple external CD32 expansion for the AUX port which will give the CD32 a few more ports and options.
If you would like to try a game that makes use of the CD32s buttons just like an arcade game, you have to try Fightin' Spirit! You can get a brand new, boxed copy still here -
http://www.vesalia.de/e_fightinspirit.htm