That’s the nearest option I could find, and I agree, it isn’t a great match, but then I don’t think anything can be.
The thing is, Karabiner is doing some low-level wizardry, and it is the only thing that I’ve ever come across that goes down to that level to do this sort of thing. Everything else I’ve ever seen always piggy-backs the work being done and has Karabiner as a prerequisite.
Personally, I’ve never used Karabiner. I rely on my more traditional key combinations, Alfred workflows, Keyboard Maestro palettes, a Stream Deck and/or Touch Bar (Better Touch Tool FTW!). I’ve got so many ways to trigger so many things (often multiple ways), that the cognitive load of adding a hyper-key with Karabiner and just the fundamental need over the hundred of options have just never taken me down that path.
As it happens, I also *really* don’t like the idea of something poking around at that level without it being part of the OS or being developed in part with Apple. I remember some of the really low-level stuff I used to use at work on Windows that IBM developed in partnership with Microsoft, and even that caused headaches in the real world a lot of the time. I don’t want those headaches any more, and this sort of app can definitely affect system-stability, which is presumably what the OP has experienced.
The issue log on GitHub also makes for very interesting reading. While it is very powerful, the developers are absolutely doing some great work, and it is an app beloved of many of the Internet’s more prominent Mac users, including yourself, some of the issues that seem to make it through put it in the ‘too risky’ bucket for me.