Low profile mechanical keyboards seem to be pretty slim pickings, still. https://www.keychron.com/products/keychron-k1-wireless-mecha... is one of the first I saw gain pretty wide popularity.
The K3 was about as close to a replacement for the Magic Keyboard that I have found, though. It's a good keyboard and if I wasn't so used to and familiar with the Magic Keyboard, I probably would have loved it. I just think the Magic Keyboard is better for my preferences.
I'm actually typing this on a Keychron K2 version 1 with Gateron brown switches, and it took a few weeks of trial and error as well as a wrist pad to be able to type anywhere near the comfort and speed of what had worked for me for years (but seemed like a recipe for disaster): hunched over my laptop's built-in keyboard and display at a standing desk, no external monitor or keyboard needed or desired.
Infuriatingly, the Keychron series' spacebar is noticeably longer than on Apple keyboards. The Keychron spacebar partly overlaps X and comma, whereas Apple keyboards for as far back as I can recall are exactly aligned with the outer edges of C and M. I also miss the Fn at far lower-left of Mac keyboards.
This was part of my "wasn't a fan of the layout" comment. The alignment of the X and Comma with the Command key, which is a key your thumb reaches to a thousand times a day, is so much more comfortable than any other keyboard I've found. And it really created some strain for me on the K3. I also wasn't a fan of the right shift being shorter to make room for the full size arrow keys (I'd rather have a tenkeyless or, preferably, the half-height keys on Apple keyboards) or of the function key on the right.
Really, I just wanted the Apple Magic Keyboard, the 60%/65% one, with a more tactile feel to it and preferably in black. I've looked at dozens of keyboards over the last 8 months and the K3 was the closest I found. So I'm just going to stick with the Magic Keyboard.
Still getting used to it over the Magic Keyboard though.