Re-sending this since it apparently got lost by the bug tracker:

 > Reverting 58430f29968a5661caff630d20dbbe7c864fe08d with current master
 > does _not_ fix the bug, so something else must be at play here too.

It turns out that the "something else" is just that

              /* Querying further backends can be very slow, so we only do
                 it if the user has explicitly requested it (Bug#43177).  */
              if (query_all_font_backends == false)
                break;

The attached patch reverting 58430f29968a5661caff630d20dbbe7c864fe08d
and removing the entity above fixes the bug on master.

martin