I am seeing many people use the Lutron Pico remotes which sound great. However, it is my understanding that a lutron hub is required. I'd like to avoid having to install another hub/bridge device.
Are there any simple remote controllers that can connect directly to HE?
Depending upon what you want or how you are using it, the RGBGenie micro remotes are close to Pico in funtionality and appearance.
But you have to consider that at some point a Lutron Bridge will pay for itself. Picos are only about $14 each, where most any other reliable (and decent looking) solution are in the $30 and up price range.
So at about a $15 savings for each remote, you can pay for a $125 Lutron Bridge at about 8-9 remotes.
I know this isn't what you want to hear, but I have a ton of button devices and was never happy until I got Lutron Pico remotes. If you have a lot, consider carefully the advice above: Picos are so cheap that the Bridge will pay for itself if you get enough of them. Even if they don't, they work so much better that I'd consider it to be worth it regardless. I moved all of my Hue Dimmers back to Hue (no problems with them there; at least one "fell off" Hubitat occasionally for some reason, not an uncommon problem), stopped using most of my Era Remotes (not bad but they take a while to "wake up" sometimes and the "hold" delay is longer than I prefer), all of my Minimotes (one of very few things available when I started) have worn out their rechargeable batteries by now, and the SmartThings Button is probably the only "good" device I'd save among the ones I've previously tried. (But it's not exactly a remote.)
Something else you could consider: many modern (last few years) Z-Wave switches now have Z-Wave Central Scene support, which on the Hubitat side basically means that taps and (in almost all of these) multi-taps can get interpreted as "button" events on the hub. Some even let you disable local control so this doesn't control the actual load, which could be useful for smart bulb control, but even with a "dumb" load you could use the extra taps for other devices. These are basically, then, hardwired remotes. These are the only other device I'd consider keeping among hte ones I've tried. Zooz and Inovelli (Red Series only) support both of these features; GE and HomeSeer support scenes (so multi-taps, poorly documented as they may be with the GE) but have no official means of disabling load control.