UPDATE: Lightroom Migration - Support cannot resolve issues. Offers refund.

After repeated efforts over several months, and seven tickets, ON1 support finally admitted that they do not have the resources to support the Lightroom migration tool and offered me my money back.

I can't say your experience will match mine, but if you are relying on this tool to move from Lightroom be aware that you may waste a lot of time with no result. If you hit serious problems you could be out of luck.

Some of the issues I encountered:

Some of the promised LR edit conversions are not applied (eg crop)
The "translated" edits are too different from the Lightroom source to be useable.
LR catalog corrupted after migration.
For ~100k images (~15k edited) the process ran for several days and filled the system disk (adding >300GB in my case) with no indication of progress or % done.
If using the "make copies" option the process stalls with all the copies still in the migration cache. (even with just 4 images in a test catalog).

Here is their final response:

"Hello,
We apologize for the ongoing hassles.
Unfortunately our dev team is unable to determine a root cause for the issues you've been experiencing with our Lightroom Migration tool and have indicated they do not have any further solutions or suggestions.
We're a small company and do our best to troubleshoot and work to correct all user reported issues. Unfortunately sometimes there is no resolve.

We can issue a refund for your purchase if you would prefer.

Our apologies, but we have no further solutions."

LR 6.14 - ON1 2022.1 - MacOS 10.14.6