I have text clippings (.textClipping) from various previous Mac systems ranging through System 8 and all the various OS X versions.
On BigSur, these appear blank. On previous systems they also appeared blank, but (weirdly) I could still cut'n'paste the text, but not with BigSur.
I've tried:
- a heavily-promoted site (loaded with annoying pop-ups) that promised to convert them online, but no result.
- using DeRez in devTools (as another answer suggested) to no avail.
I do have older Macs with previous OS X versions, but I really need a way to extract the text from a modern Mac - there must be a load of people with the same issue!