There's a similar issue for cfsolrlib on GitHub running on Lucee 5.x:
AFAIK, JAR files and JavaLoader should still work in Lucee 5.x just as they did in Lucee 4.5.x. It looks like the Tika constructor is overloaded, so I'm not sure if this is a Lucee bug in how the constructor is being called -- but it looks like that error message does come directly from here:
I'm not sure how the MagicDetector gets configured/initialised -- it could be something to do with configuration, or perhaps it is indeed a Lucee 5.x related issue. I wonder if @jeff or @seancoyne have any ideas?