I hadn't tried leaving the trainer running yet not activated approach. It had been closed each time before I began my next attempt. Sadly, it didn't work for me. I got the Unknown file version C:\program files (x86)\steam\steamapps\common\FarCry5\bin\fc_m64dll error again.
oh well, had a sparkle of hope for a minute there.
I had the same problem, what worked for me before running the trainer, ad an exception in windows defender, paused Kaspersky and killed all uplay processes via Taskmanager. After that it worked without a hitch even though I had multiple monitoirs, odd install dir and uplay in online mode