Edit: For anyone who might also come across this issue, stop baloo service with balooctl disable and delete the contents of ~/.local/share/baloo. Now go into System Settings-->Search-->File Search and delete all folder specific configurations before re-enabling with balooctl enable.

Hope that helps someone!

sothis6881 is there any upstream bug report, so to see if can backport code but couldnt find anything? Additionaly I do not have this issue

      Girtablulu Thanks for checking! I couldn't find any either, so it might just be me. I thought I resolved the issue on my Arch install, but it returns after resuming from sleep. Go figure...

          sothis6881 Can you check via terminal if you really fully up to date and if you may have any borken packages? If everything is fine and it's still happening an upstream report would be welcomed

            I ran eopkg upgrade and eokpg check and everything seems fine. Is there anything else I should do via terminal?

            I've tested this now using several different distros both in Virtualbox and on two separate bare metal installs. Some distros don't even show the "Modified Today" in Dolphin at all. I wonder if this feature was simply dropped. If so, I'm really disappointed because I use that feature every day.

            11 days later

            There's now a series of bug reports with similar/related issues.

            Bug 430273 - Index breaks regularly

            Nate Graham 2020-12-23 23:50:26 UTC
            (In reply to pipapo from comment #12)

            Purging the index did not fix it. baloo breaks again when you logout and
            login.
            baloo is working as expected after getting and installing
            baloo-kf5_5.77.0+p20.04+git20201219.0226-0_amd64.deb
            libkf5baloo5_5.77.0+p20.04+git20201219.0226-0_amd64.deb
            from neon unstable.

            The fix is in 5.78, not 5.77.

            12 days later

            Hi folks,

            Were the latest updates this Friday which included some baloo updates intended to fix the recent search problem?
            I still have the Dolphin search return nothing since the update. I'm wondering if I need to clear out the baloo .local file and restart the service as above?

            EDIT
            Update - I went ahead and stoped the baloo service, cleared the local database etc and restarted the service as described sothis6881 above. Seems to have fixed it and persists after reboot so maybe mark solved.

              vyzle yea you need to purge the index, they corrupted it with an update but this got fixed on 5.78 and they looking into a way now fixing it automatically without having the user to run the command manually

                Glad it helped and happy that the fix came with Frameworks 5.78.

                vyzle I discovered as a shortcut you can delete Baloo's index with balooctl purge