Options exist for all three of them.

For a trackpoint version, checkout the buzzard. I also recently added beta-level support for trackpoints to zmk. So you can build a wireless trackpoint split keyboard.

I am also working on a corne clone with trackpoint support.

You can come to the zmk discord pointing-devices channel to discuss the topic with more people.

You can hook up a trackpoint module salvaged from a thinkpad keyboard to a Pro Micro, and use that in a handwired build. See e.g. [here] (https://community.keyboard.io/t/trackpoint-mod-ii-a-new-guide/3663) or [here] or here (https://rfong.github.io/rflog/2021/10/26/r61-trackpoint-pt2/). You can use it with QMK, see here, see also this build.

Not ergo, but there are the Shinobi and Shura from TEX.

Shirogane Lab's Keyball has the most elegant integrated trackball situation, IMO. I thought I heard somewhere that it was an open source design but I haven't been able to find the socket. If your keyboard can support it I think mouse keys are really nice too.

I know there's a small I2C module you can get with a miniature trackball like the ones that were popular on certain models of blackberry phones around 2010 or so. I found it being sold on pishop, but the silkscreen on it says its made by pimoroni.

check out https://www.reddit.com/r/trackpoint_builders

HolyKeebs just announced their new keyboards with integrated trackpoints: https://holykeebs.com/pages/trackpoint . Something they do that is really cool is build them into the microcontroller itself, so if your board has the microcontroller in a convenient place, you can add the trackpoint straight to an existing device (already sell it for pimoroni trackballs, trackpoint in Q3). I have a Corne from him with the pimoroni, and I enjoy it, but the pimoroni is not a full mouse replacement for me.

Another option is the cirque touchpads. I've not tried them but they are popular and people find them usable enough as an actual replacement primary pointing device, which isn't the case with things like the pimoroni trackball, etc.

Check out Bastardkb Charybdis ;)

There’s a more active discussion in the ZMK discord on pointing devices: https://discord.com/channels/719497620560543766/845285481888743434 or click the discord link on https://zmk.dev/ See also the trackpoint_builders subreddit.

My personal bias is still using a separate trackpad, but have thought about doing something like a cirque with haptic feedback.

I've had a few different boards with integrated pointing devices now. The Dilemma from Bastardkb, the charybdis nano from Bastardkb, and Frigate from keyboard dweebs. End of the day, they're nice but can't compare to split + apple magic trackpad for me personally. The alternatives feel like I'm giving up so much fine control and surface area for not much gain.

On that note I do have some of those boards still I can sell for pretty cheap if you're interested.

I like split keeb + large trackpad + mouse

Trackpoint? You mean the clit mouse.

https://github.com/alonswartz/trackpoint is one data point. I don't know where exactly you're supposed to get the trackpoint module.

There are all sorts of Corne variants, as I recall, where circular trackpads are added. Some Dactyl Manuform forks add a trackball.

Beekeeb announced getting a mini trackpad working

https://beekeeb.com/cirque-trackpad-i2c-on-corne-keyboard/