The application of a recently demonstrated mode-locked ultralong pulsed fibre ring laser architecture (Gallazzi et al., 2021) to the inexpensive and efficient generation of supercontinuum from a pulsed output at 1.56 μm in standard single-mode telecommunication fibre is experimentally demonstrated. The impact of broadening fibre, dynamic switching between different harmonic modes and the influence of laser polarization on the properties of the generated supercontinuum are studied for three different kinds of telecommunication fibre. Flexible spectral broadening beyond 200 nm is obtained with good temporal correlation and pulse compression from 240 fs down to 50 fs.