I think mechanical keyboards are just too high, with excessive travel. You sort of have to keep your hands floating in the air, which transfers stress to your neck, shoulders and upper body. No palm support I tried offered any substantial relief, probably due to the long travel and finger contortions required.
Second issue, perhaps I'm a poor typist, but my fingertips frequently got stuck between the keys, causing mistakes by triggering adjacent keys.
One day I got tired and bought a 10 euro keyboard from the grocery shop. Noname, slimline, rubber domes. What a relief that was.
These days I swear by Logitech MX Keys. Best keyboard I have ever touched.