With regards to ergonomics, I don't think the Planck solves really any of the issues with a standard keyboard. While the straight columns and rows might reduce some horizontal movement of your fingers when typing, the fact that it's one piece with no angle means that your wrists will be contorted, which is the same problem with a standard keyboard. Also, your fingers aren't the same length, so having ortholinear keys doesn't really account for that in any way and pinky finger keys are more difficult to access.
If you're going to bother with learning how to type on an unconventional keyboard (and if you have any sort of concern for your wrist/hand health, I'd encourage you to do so), I'd suggest looking at split keyboards what have offset rows with straight columns of keys, at the minimum. ZSA actually sells the Ergodox EZ and Moonlander, both of which I'd say are better keyboards. They are of course a lot bigger than the planck, which might be problematic if you're using it on the go a lot.
If you're looking for something a bit more portable, perhaps something like the atreus would be more suitable. There's a prebuilt one you can purchase from keyboardio [1] though you can find kits online to build one yourself. Gboards [2] also has some nice low profile small form factor keyboards, though the owner of Gboards is currently not accepting any new orders as she's working through the backlog of orders. There's a ton more shops that sell kits for small form factor keyboards and there is no shortage of choice for keyboards with all sorts of form factors and numbers of keys. A good place to start researching it is the ergonomic mechanical keyboards subreddit [3] and the olkb (planck) subreddit [4].
Personally, I use the Kinesis Advantage 2 [5] with a custom microcontroller designed by Michael Stapelberg [6] that allows me to run QMK [7] on it. Kinesis has announced a new fully split keyboard that doesn't have a ship date that I'm also very interested in [8]. These have concave key wells which are a bit hard to describe but once you've put your hands on one, it becomes pretty obvious the difference in just pure comfort to the hands they bring. Any keyboard with these key wells however are very large and not exactly a great portable keyboard. Still, I think the tradeoffs are well worth it.
Finally, If the Advantage isn't your jam, there are open source keyboards made with key wells and are fully split like the Dactyl [9], and Dactyl Manuform [10]. Prebuilt manuforms can be found at Oh Keycaps [11] and a few other vendors. These are very geeky keyboards that will require a lot of effort on top of the effort of learning how to type, so I'd only suggest them if you're really ambitious about using alternative keyboards and getting the most out of them.
A lot of the more popular mechanical keyboard communities are great for what they are, but they have kind of zeroed in on focusing on mostly aesthetics. The Mechanical Keyboards subreddit [12] is primarily glamour photos of people's keyboards and offers very little discussion in terms of ergonomics, alternative keyboard layouts, or other aspects of the hobby. Still, it's a great place to look for key switches you might like (the sound being one of the big considerations) or keycap group buys that you might be interested in. I hope that I can help get more eyes on the ergonomic keyboard community since more eyes is more interest and more interest means more innovation and better keyboards.
[1] https://shop.keyboard.io/products/keyboardio-atreus
[3] https://www.reddit.com/r/ergomechkeyboards
[4] https://www.reddit.com/r/olkb/
[5] https://kinesis-ergo.com/shop/advantage2/
[6] https://michael.stapelberg.ch/posts/2020-07-09-kint-kinesis-...
[7] https://qmk.fm/
[8] https://twitter.com/kinesisergo/status/1397335511694381058
[9] https://github.com/adereth/dactyl-keyboard
[10] https://github.com/abstracthat/dactyl-manuform
[11] https://ohkeycaps.com/products/built-to-order-dactyl-manufor...