Rockymounts Clutch SD (now called the "Driveshaft HM"):
These can do 20mm thru-axle, 15mm thru-axle, and 9mm skewer/QR - super versatile. They're built really strong (they're heavy!), the bikes don't move or sway at all when mounted, and the built-in key locks sealed the deal for me.
They have less expensive ones that only do 9mm QR, but since I mountain bike I needed this one.
I have a very similar mount, made by Rocky Mounts. What I like most is that the center bolt that holds it in can't be accessed by a Torx tip when it is locked. The locking latch folds down in front of it. So someone can't steal the mount even when my bike is out of it.
I ended up taking someone else's idea from here and made this bike mount. Delta Bike fork from Amazon for 15 bucks, spring nuts from Lowes or HD for 4 bucks and some bolts and washers for a buck. So 20 bucks for one. Ended up making 2 for me and my wife's bike and it works great, no issue at all.