Did you make sure you updated the CIA? Use Homewbr3w, the homebrew browser, to do it (
https://gbatemp.net/threads/release-homebr3w-simple-homebrew-browser-and-installer.434105/).
I checked my Luma settings, I'm on 11.3, all my homebrew is up-to-date, and the Homebrew Launcher loads perfectly fine for me.
Since I have no idea about what you have installed or deleted, there could be a number of other potential problems.
It's true that the guide says Clock+L2 breaks HBL support on 11.3, but HBL was updated just over a week ago with 11.3 compatibility. The latest hourly build of Luma will apparently fix it, so that's probably what you've missed. I saw recommendations to update to the latest hourly when 11.3 came out, but I thought that was a given considering how Luma hasn't had a stable channel update for a month or two.
This might interest you:
https://github.com/yellows8/hblauncher_loader/issues/63