Try this one. A python plugin. Modified from one I use as a 'quick-save' for the open image.
Download, unzip, put jpg-to-png.py in C:\Users\"yourname"\AppData\Roaming\GIMP\2.10\plug-ins
Registers in the Tools menu. Tried in Win10 / Gimp 2.10.22 and works there.
There are caveats:
It can have a hotkey assigned to avoid going into the menu every-time.
Providing no other plugin has been used in the meantime, Ctrl-F repeats the last used.
Download, unzip, put jpg-to-png.py in C:\Users\"yourname"\AppData\Roaming\GIMP\2.10\plug-ins
Registers in the Tools menu. Tried in Win10 / Gimp 2.10.22 and works there.
There are caveats:
- The first use in any particular Gimp session, set an output folder, otherwise you get an error. I think worth keeping to separate the files but it could be the folder containing the jpegs. Subsequent use keeps that path.
The filename has an underscore appended ie. filename.jpg becomes filename_.pngEdit: Dear me, I am dim, fixed that.
- Guarantee, there is no guarantee.
It can have a hotkey assigned to avoid going into the menu every-time.
Providing no other plugin has been used in the meantime, Ctrl-F repeats the last used.