The xwhatsit controller supports buzzers directly and some types of solenoids through the solenoid driver add on board.
admin edited answer
As an update, solenoids are now available to order! They work on any xwhatsit Model F or xwhatsit beam spring keyboard! Each solenoid requires a solenoid driver too.
More details here: https://www.modelfkeyboards.com/product/xwhatsit-beam-spring-or-model-f-controller/
A Deskthority user has added a solenoid to his Brand New Model F Classic Case Keyboard https://deskthority.net/viewtopic.php?f=62&t=23707&p=462600&hilit=f62#p462600