6
Checklist software
(lemm.ee)
If it's free and open source and it's also software, it can be discussed here. Subcommunity of Technology.
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Joplin. Just make a note. I think they have a to do list feature too but I just make a regular note myself.
There are two ways to do a to-do list in Joplin: within the text of a single note or at the next level up, where an entire folder can be populated with full-fledged notes you can individually check off. The flexibility is really nice.