Having tendon issues in my wrists, I would love a linear keyboard with gentle push down force. Or at least just gentle push down force. Any suggestions?
The Gateron Clear switch is the lightest linear switch currently available, with an actuation force of about 30g - half that of a typical membrane key switch and 50% less than the Cherry MX Red linear switch. It's not a particularly popular switch, because it's so light that the weight of your fingers tends to cause accidental keypresses on the home row. Nonetheless, you can buy a KBParadise V60 keyboard with Gateron clears. The Qisan Magicforce 68 is occasionally available with Gateron clear switches. Alternatively, you could buy the keyswitches and build a keyboard to your own specifications using a bare keyboard PCB.
Seconded Gateron Clears (though I've heard the activation force is more like 35g than 30g). I use them on a Noppoo Choc Mini.
I'm a fast typist (around 130wpm) and use these switches just to try to improve speed, rather than anything relating to health. They're also great for gaming for me, playing Starcraft 2.
Has Cherry Red switches. I've been using an advantage for probably going on 20 years at this point, but I'm not going to lie, it took a fair amount of time to adjust to it's non staggered layout (the wells and thumb clusters are easy to get used to, but you have a lot of staggered muscle memory if you touchtype).
So if you aren't ready to take the "crazy layout" plunge but want low force switches, MX Reds are really light and really linear.
You can even go further and try Cherry Silvers, I believe they are essentially the same (same spring weight, same linear stem) but the actuate at 1mm instead of 2mm (most cherry switches have 4mm of total travel).
Cherry MX Red switches are probably what you want, there are tons of keyboards with cherry switches and frankly not a whole lot of difference between them in terms of typing experience. Corsair K66 is a decent example, one of the cheapest at $60 from amazon currently and doesn't have the ridiculous "gaming aesthetic" that plagues so many mechanical keyboards.
Cherry Red switches are linear with light force. I was having some finger joint pain for a while, and bought keyboards with both Cherry Reds and Cherry Browns (similar but with a slight force bump). It took a little while but I trained myself to type on these without bottoming out the keys. My finger problems cleared right up, and as a bonus I ended up typing faster.
http://www.mechanicalkeyboards.com/shop/index.php?l=product_...
https://www.ebay.com/itm/Gateron-Clear-switch-3-pin-for-mech...
https://mechanicalkeyboards.com/shop/index.php?l=product_det...