A reasonable response would be ‘RTFM’; I did, but didn’t find the info I’m looking for, which I’ll try to clarify:
Based on sound advice, mainly from this service, I am quite used to regularly backing up the files which darktable keeps as it’s ‘brains’ – i.e. all those in ~/.config/darktable (linux) or AppData\Local\darktable (Windows). I’ve started using RawTherapee a lot more recently and realised I needed to do comparable backups, but all I can find is in ~/.config/RawTherapee-AppImage (linux) or AppData\Local\RawTherapee (Windows). I find no equivalents to (for example) darktable’s data.db or library.db, darktablerc or luarc.
So where does Rawtherapee keep it’s equivalents – or are there none? Does it just load the sidecar file (.pp3) for each image singly, on demand? What else should I be backing up in rawtherapee (ignoring the images themselves)?