Unfortunately, when attempting to use krunner to launch a search (here) it fails… and I am unable to work out what’s wrong.
I’m curious if an update to Discuss caused the failure, and disappointed to note that it isn’t updated in the Web Search Keywords.
The nearest I got was https://discuss.kde.org/search?\{@} which presents me with the searchbox.
Works for me with https://discuss.kde.org/search?q=\{@}
Thanks for that… I was ‘q’ jumping 
So basically, all those URL’s need updating for KDE stuff… I guess it’s a lesser known or used feature so it got less attention.
Adding a KDE Discuss search would make for a good simple contribution!
I wrote a blog post about web shortcuts a few years ago. I also just merged two small fixes today, one of them is as simple and tiny as Add Fedora Packages search (!1818) · Merge requests · Frameworks / KIO · GitLab. The feature is kinda underappreciated still, I really love this feature.
If you want to make a contribution the right place for the file would be src/urifilters/ikws/searchproviders · master · Frameworks / KIO · GitLab, and the file is usually installed on /usr/share/kf6/searchproviders (it used to be /usr/share/kservices5/searchproviders in Plasma 5). For testing you can just create a desktop file there then restart KRunner (systemctl restart --user plasma-krunner).
If you don’t know how to make an MR we have Infrastructure/GitLab - KDE Community Wiki.
