The GSC DORIS analysis center has contributed to DORIS processing for ITRF2008, ITRF2014, and ITRF2020. For ITRF2020, we processed data from 1993 to 2020 with a variety of improvements, new versions of GEODYN, and a series of new satellites. We summarize the improvements that were made regarding the DORIS processing w.r.t. the previous ITRF submission, ITRF2014. The improvements included updated background models for gravity field (static & time-variable & atmosphere-ocean dealiasing products), application of new elevation-dependent data-weighting functions and the lowering of the cutoff angle to 7 degrees, and the improvements to the non-conservative force modelling. We also discuss the further changes that have been implemented since the completion of the ITRF2020 submission, and assess the contribution of Sentinel-6A to the DORIS combination.