The Debian packaging of debug-me is maintained in git, using the
merging workflow described in dgit-maint-merge(7).  There isn't a
patch queue that can be represented as a quilt series.

A detailed breakdown of the changes is available from their canonical
representation - git commits in the packaging repository.  For
example, to see the changes made by the Debian maintainer in the first
upload of upstream version 1.2.3, you could use:

    % git clone https://git.dgit.debian.org/debug-me
    % cd debug-me
    % git log --oneline 1.2.3..debian/1.2.3-1 -- . ':!debian'

(If you have dgit, use `dgit clone debug-me`, rather than plain `git
clone`.)

A single combined diff, containing all the changes, follows.
--- debug-me-1.20181208.orig/debug-me.init
+++ debug-me-1.20181208/debug-me.init
@@ -33,7 +33,7 @@ case "$1" in
 		start-stop-daemon --start --quiet --oknodo \
 			--background --no-close \
 			--pidfile "$PIDFILE" --make-pidfile \
-			--chuid debug-me:debug-me \
+			--chuid _debug-me:_debug-me \
 			--exec "$DAEMON" -- $DAEMON_PARAMS \
 			> /var/log/debug-me.log
 		log_end_msg $?
--- debug-me-1.20181208.orig/debug-me.service
+++ debug-me-1.20181208/debug-me.service
@@ -8,8 +8,8 @@ EnvironmentFile=-/etc/default/debug-me
 ExecStart=/usr/bin/debug-me $DAEMON_PARAMS
 InaccessiblePaths=/home /etc
 ReadWritePaths=/var/log/debug-me
-User=debug-me
-Group=debug-me
+User=_debug-me
+Group=_debug-me
 StandardInput=null
 StandardOutput=journal
 StandardError=journal