Ergodox's Alps compatibility was discovered by chance... They pin holes are not perfect but having a plate (which you would need for Alps anyway) would force the switches to be oriented correctly.
There are lots of vintage ergonomic keyboards with Alps, but I don't know of any that is truly split.
Filco Stealth, Datadesk Smartboard, Omnikey Evolution, Chicony/Addison KB-7001. Then there are some Japanese M-system (M-Shiki) keyboards with Alps, but they are very rare outside Japan, and I don't know how to make any of them work with a modern computer.