Sadly currently you cannot view issues in the bugtracker if you have a simple custom CSS!

Some games need customizations due bad contrast with many players (many player colors ->white on bright background for instance) Or Ticket to Ride: Europe Big Cities when you have 20+ tickets fulfilled need to shrink and wrap the fulfilled/unfulfilled tickets to fit on screen.

Then you are forced to use Browser extrensions like "Stylus" for Firefox or Tampermonkey.