Well, I got a little trick. I got a very old image viewing program (once installed under Windows 98 to give you an impression of how old it is) I copy&pasted the program files from drive to drive and for unknown reasons reasons it keeps working (to a fashion, occasionally it does crash but by and large it does what I want)
And when I now open an image I saved from the internet with it and choose the option
save as jpeg it does so of course, even if the image is already a jpeg (though I do rename it a bit just to be safe) and often enough the newly created jpeg has a much smaller file size (up to 80% smaller) without losing much (or any) detail. I have to admit that occasionally there is a notable loss in detail or the filesize didn't get much reduction, but for most images it does work satisfactorily, bringing down the file size to levels which can be attached here.
So maybe see if you can get an old image viewer this might do the trick.
Image kinda related to topic
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