;)
Your mission, should you choose to accept it, is to develop a "manual" typewriter that warns the user that they are about to make a spelling mistake, possibly keeping the whole word in a buffer until they handle the warning. The warning itself can be performed via any means, including but not limited to an electrical zap.
At some point there used to be electric typewriters with a 1 or 2 line buffer that they'd show on a black and white LCD. I don't know whether they had a spellchecker, but it wouldn't be hard to add one.
Except, you'd need ~50KB of ROM to store an English dictionary. This figure comes from the original UNIX spell program, which employed advanced compression techniques to fit into a 64KB memory footprint: https://ieeexplore.ieee.org/document/1095395
It would if they didn't have sufficient compute, RAM, ROM.
Something that can buffer and edit 2 lines (~160 byte, and not necessarily 8-bit ones either) does not necessarily want to add hundreds of kilobytes of dictionary and the code to look things up in it.