I’ve been using split boards since the original Microsoft Natural Keyboard, the one with the awful number pad. Then a Kinesis Advantage, then the 360. The DIY boards like a Lily58, Corne and a similar custom are mostly for travel.

Switching to split or ortholinear takes time. Doing both together is a significant and slightly annoying adjustment and takes a few weeks to feel normal. The payoff is when you lean into it. Home row mods so the home keys become ctrl shift alt meta when held, plus a thumb layer for navigation so you get vim-style movement everywhere, and a symbols layer for the stuff not on the top row.

Two thumb keys per side works well. Layer on both sides, enter on one thumb, space on the other. About 6x4 per side is the sweet spot for me. A function row on things like the Advantage 2 or Glove80 can be handy.

If you want to try it in steps, the Kinesis mWave is a decent bridge. Split but not ortholinear, full keyset so you don’t have to relearn everything at once, mechanical, runs ZMK, and in US pricing it’s very cheap for what it is, roughly $120.