TLDR; Enabling 'Use old Start10 style search' breaks the search functionality in Start11 1.1 (Windows 11 Version 21H2 (build 22000.434).
For me, search is not working. I have indexing enabled in Windows settings, as well as 'Search for file contents as well as names' in Start11. I tried restarting File Explorer via Task manager, then the search worked. As soon as I closed start menu and went to search again, it had stopped working. The space where search results should appear is completely blank but some times I see a gray text saying 'Searching' or something like that. I'm using Start11 version 1.1. I did not have this problem in the previous versions. I'm using Windows 11 Version 21H2 (build 22000.434)
A few moments later:
I think I figured it out: I've enabled 'Use old Start10 style search'. As soon as I disabled that, search started working, but using the Windows 11 search. So there's your bug. Would be great to have old style search working, I like its minimalistic look.