This year I found ustaxes.org (AGPL) which could handle federal taxes. For state I used the same method I've heard Stallman uses. Downloaded the form(s) I needed as PDFs (weirdly hard to find, after getting lost on the official site, I found them on another site that just collects and hosts tax forms) and modified them with xournalpp. The remaining gotcha is that I didn't know how to e-file in a libre way, so I had to print off the documents to mail them. I would very much like to see things improve more in this space. I believe I had very simple taxes, and I didn't much care about how much I got back. I would gladly give up the potential return to not have to do this at all.