I really want to be able to use Nik plugins but even rolling back to Nik 4 hasn’t solved the problem(s). I keep verging between abandoning Nik Collection and trying to get it working.
I don’t use PS much, but I am on Adobe’s photography plan so I have it. I think I might give your workaround a try i.e. creat new TIFFs in PS first - it’ll be a bit ‘painful’ but I can live with it if it works. I’ll let you know!