From the old Welsh forum, posted on 17th March 2022:
The free pdf files of the current course books mentioned by rmcode are here - https://dysgucymraeg.cymru/dysgu/cwricw ... wrslyfrau/
Printed copies are available for, I think, £10 each - but check that you are ordering the very latest versions. The 'new' Mynediad book was revised again last year, and some bookshops are still selling the old WJEC-based course books which have not been used on DysguCymraeg courses for quite some time.
This Duolingo course broadly covers the material in the Mynediad A1 and Syflaen A2 courses, and some material from Canolradd B1.
As at mid-March 2022, the changeover to the updated Duolingo course has only been applied to a proportion of Duolingo leaners. If all goes, well, more and more people will gradually be moved over to the newer version.