hi,
Loook is a fantastic tool! Yes,with absolutely 3 “o”-s… Loook…
many Linux distros have in in their repo despite it never reached v1.0!
cause it is perfect already
however, some weeks ago it started a strange behavior,
when clicking on a document, it would no longer open…
nothing happens…
then you realize that it must be the viewer, a key parameter, which might cause this
originally it is set to “soffice”…
anyway, I’ll cut is short:
open Writer and look at “Paths”…
and under “internal paths” you’ll find lots of paths like “/opt/libreoffice7.4” FOR EXAMPLE 
the solution is to take this path to libreoffice… copy and paste it into the viewer field (at the top of the LOOOK UI)
one more piece of useful info:
when you change the “viewer” field’s content, you can already click on the files in the matches list,
LOOOK will know which application to open them with (if it is successfully defined)
so, once again this info is for people using Linux, Debian, for example… (my case)
Despite I’ve already explained how to solve this, I leave this open for answers …
cause I can imagine better explanations than mine