hi, welcome.
i can reproduce the difference between searching “onlyoffice” from the home view vs from the all applications view… i’m using kubuntu LTS 24.04 so discover 5.27.12
if the former, i’m presented two entries, one that defaults to flathub and the one from snap… the one showing the flathub option, will show the snap alternative under sources, but the one showing the snap just says install.
in the latter i’m presented with only one entry in the search result, but when i go to the page i have both sources to choose from (default is flathub).
not sure why this difference exists, but you can definitely get to either option from either starting point, so i don’t consider it a fatal issue.
as for apt packages not appearing in discover… the discover store is a GUI browser for GUI applications, so i would not expect to find say lm-sensors in discover since it’s not a GUI application.
for a GUI interface to the other apt packages, would (use discover to) install the synaptic application and use it’s search feature to find what i need.
i could not reproduce your issue with gimp… for me the search results are the same no matter my starting point and when i enter the page i can see both the native and flathub versions under sources…. this could be a non-LTS track specific issue that will likely get sorted when the next LTS releases next april.