https://writing.stackexchange.com/a/442/49757 says "For tracking short stories and direct submissions to publishers, use Duotrope, a free online tool that contains every market you've ever heard of and a multitude that you haven't, complete with submission history, links to websites, etc. " but this would seem to be out of date information.
Duotrope is not free at the moment, but there is a supposedly free service called Duosuma which is short for "Duotrope Submission Manager" but I am finding it hard to understand what exactly one can do with it for free. If you try to get Duotrope for free you are offered Duosuma which is owned by Duotrope I think, though it is not clear to me what the exact relation to Duotrope is, but it seems to me that Duotrope is in some sense the premium version of Duosuma.
Is Duosuma really free and if so what exactly can you do and not do with it for free and for how long?
I am a writer and so I want to use Duosuma as a writer and that is what the question is asking about, in case I didn't make myself clear.