Lord of the Rings Online cannot launch

Lutris has been very effective so far. I’ve installed it and used it to get LOTRO running about a half dozen times. But now I’ve got a weird error on a system that I upgraded from Devuan 3.1 to Devuan 4 and then used the ‘add game’ button to import the game rather than reinstall. When I try to run the game it starts the launcher and begins the usual preliminary checks, but halts with an error:

“PatchClientDLL:CheckDatFiles Failed.”

What could this mean? I’ve not only replaced the named file, I’ve copied a full working install from another machine to make certain none of the files could be corrupt. No difference. This same error pops up every time. It worked fine in Devuan 3.1 so I am guessing it has something to do with the differences between the versions.