LR6 upgraded "automagically" to LR8 - what are my roll back options?

on your computer use Windows file explorer, or MAC Finder, bring up the directory your Lightroom catalog is in, share a screenshot of that.

Question. The upgrade from your LR 6 perpetual license to Lightroom Classic should not uninstall the LR 6 installation on your computer  however to run Lightroom Classic on your computer it would have prompted for it to create an copy of your Catalog file. If you did not uninstall LR 6 you should still have access to that application and the last Catalog file used. Before offering advice other users will need to know the answer to this info. 

leml73055714  wrote So basically my options were to buy LR subscription or to lose all my changes for 3 years. As much as I love LR, I'm not amused by the Adobe marketing strategy here... Rant ends. Does anyone know if there is a way to convert the catalog from LR8 to LR6 and, if there is, what changes would be lost in the process? Cheers,

It's not possible that you have lost 3 years of changes. Why? Because the version after LR 6 didn't become public until about October 2017. It's also not possible for you to use a "trial" to the newer version for a whole year.

But, regardless, your catalog is not backwards compatible with LR 6. You could transfer the edits and metadata backwards to a LR 6 catalog via this procedure, however, not everything will transfer this way. Specifically, collections will not transfer, pick flags will not transfer, edit history will not transfer (but the final edited image can be transferred except for new editing features available in LR 7 and LR 8), and there are a couple of other things that will not transfer this way (I no longer remember the complete list of things that won't transfer).

Here's the method:

1. In LR 8, select every image in the Library Module (Ctrl-A) and then Metadata->Save Metadata to File. I have no idea how long this will take, you might as well start it before you go to bed and let it run all night.
2. Your LR 6 catalog should still exist on your hard disk somewhere. In LR 6, open your LR 6 catalog and import images that have never been imported previously into your LR 6 catalog using ADD. Then select all images (Ctrl-A) and Metadata->Read Metadata From Files. (Alternative: you could start a brand new LR 6 catalog, and then import every image into this new catalog using ADD, then if necessary Metadata->Read Metadata from Files).