The only rift lake eel i can think of off the top of my head is Mastacembelus moorii and Mastacembelus plagiostomus. They are not from Lake Malawi, only Lake Tanganyika. They are notorious fish eaters and should probably be kept in a species tank. You would probably only be able to keep them with large Frontosa or maybe Boulengerochromis microlepis, but Boulengerochromis microlepis isn't suited for a tank any shorter than 5m (they get over 90cm).
If you are interested in a cichlid setup, decide whether to go with Malawi, Tanganyika, or rivier cichlids. I wouldn't keep anything that doesn't originate in Malawi with a Malawi/Mbuna setup (mixing lakes/regions in general is a bad idea).
(Upon a quick google search it turns out that Aethiomastacembelus shiranus is a eel native to malawi)