I waited 7 weeks for reply from ufile to my problem I filed with them but got none. Faced with June 15 2022 deadline, I proceeded with AnnaT's solution above and it appears to have worked (list of tax slips from 2020 now there).
But I am now forced to pay for 2021 a second time before I can see the return. I will be asking ufile for a coupon for next year.