I found these NGINX rules elsewhere on the forum; I don't know if they are 100% correct, but they should at least help anyone who find this thread in their journey
rewrite entries/([0-9]+)(?:/?$|(?:-[^/]+))(?:/?$|(?:/page([0-9]+)?)) entry.php?b=$1&page=$2&$query_string;
rewrite threads/([0-9]+)(?:/?$|(?:-[^/]+))(?:/?$|(?:/page([0-9]+)?)) showthread.php?t=$1&page=$2&$query_string;
rewrite members/([0-9]+) member.php?u=$1&$query_string;
rewrite forums/([0-9]+)(?:/?$|(?:-[^/]+))(?:/?$|(?:/page([0-9]+)?)) forumdisplay.php?f=$1&page=$2&$query_string;
rewrite blogs/([0-9]+)(?:/?$|(?:-[^/]+))(?:/?$|(?:/page([0-9]+)?)) blog.php?u=$1&page=$2&$query_string;
rewrite list/([^/]*/)([0-9]+) list.php?r=$1$2&$query_string;
rewrite content/(.*) content.php?r=$1&$query_string;
rewrite widget/config/([0-9]+) widget.php?r=config/$1&$query_string;
rewrite clientscript/(.*) /clientscript/$1; # fixed some beta 4 issues