I don’t remember where I saw this fix (probably on this very forum), but the temporary fix is to comment out the submenu line in your custom service menu.
Change this:
X-KDE-Submenu=Convert Image(s) To...
To this:
#X-KDE-Submenu=Convert Image(s) To...
On Arch Linux, there was a recent update to KIO that fixes this issue (kio 6.29.0-1 -> 6.29.0-2), but as a KDE Neon user, you may have to wait a bit.
TIP:
- Open all your service menu files in Kate all at once
- Go to “Edit” > “Find in Files”
- Select/Copy “X-KDE-Submenu” to the “Find” box
- Add “#X-KDE-Submenu” to the “Replace” box