Disable entries in the context menu:
Menu > Settings > Configure Dolphin… ( Ctrl+Shift+, ) > Context Menu
Uninstall Dolphin plugins/services:
a) Enter Dolphin’s settings as described above.
Click on “Download New Services…”, then set the filter to “Installed” and choose which ones to remove.
b) Use Discover. Select “Installed” in the sidepanel, then search for “Dolphin”. Remove the plugins you don’t want.