Every “split” mechanical keyboard currently being sold that I know of

Kinesis Freestyle (Terrible key switches. Mushy and un-lovable)

Kinesis Freestyle Edge (Traditional layout with too many keys, mech switches, proably too big to be tented easily/properly)

Matias Ergo Pro (Looks pretty great. Have not tried.)

ErgoDox Kit (Currently, my everyday keyboard. Can buy pre-assembled on eBay.)

ErgoDox EZ (Prolly the best option for most people.)

Diverge 3 (Looks great. Might buy one. Ergo-dox really has too many thumb keys anyway. This might be a better design.)

Diverge TM 2 (Cool idea. Magnets! Too few keys for me.)

Keyboardio (Halves can optionally be separated. Looks promising, but too few keys)

Dygma Raise (Nice thumb keys layout, but no arrow keys and probably too big/unweildy for effective tenting)

UltraErgo (Does not appear to be mechanical)

Ultimate Hacking Keyboard (Small layout, mech switches, intersting-looking thumb attachments but missing arrow keys! And Kinda ungly)

Lets Split (Dunno what this is yet)

Mistel Barocco (no arrow keys, but looks good if you like 60% keyboards)

Goldtouch (Technically one-piece, but close enough. I’ve used these. They’re crap.)

Goldtouch Go (Technically one-piece, but close enough. These are also crap.)

Comfort Keyboard Split Magic Keyboard (This looks terrible)

SafeType Keyboard (Also looks terrible)

Axios (Something gloriously weird that is under development. Maybe.)

Cheap Split PCB Boards for sale (Totally DIY. Soldering required!)