For odoo14:

1.-Put this ,on the line you want to stop, in the xml file.

<t t-debug="pdb"∕>

2.- Run the server:

python3  ./odoo/odoo-bin -c /etc/odoo14.conf --dev=qweb

3.- Look at the terminal, when you launch the corresponding qweb template. The debugger will stop the program where you put the tag from step 1.

4.- If you want to see the variables type in the terminal:

locals()

The Breakpoint only works when the Server is started with the command line argument --dev=qweb 

Essentially the expected behaviour is that the server would breaks and debugging would be possible from the shell from whence you ran the server.  The debug directive doesnt seem to work on qweb reports too. 

try locals()