It works setting the option --ciphers DEFAULT@SECLEVEL=1 like in curl https://www.upward.net/ --ciphers DEFAULT@SECLEVEL=1
Not sure if this is the desired behavior, since it was very difficult to solve. See https://curl.haxx.se/mail/archive-2020-05/0005.html for further information
signature.asc
Description: OpenPGP digital signature

