I use a bullet journal.
I find that I can do the product and project planning much more efficiently with a pen and paper. Something about getting my eyes off of a screen really helps me refocus my thinking. I really like that, with a bujo, you have to periodically make an intentional decision whether to retain or forget any un-completed to-do items. (I've yet to find a technological solution that doesn't make it way too easy to accumulate clutter.) I like that the limited space forces me to focus on the essentials of each item, which helps me to stick to the agile principle of delaying decisions to the last responsible moment.
I don't bother with swim lanes, columns, task states, or anything like that when I'm working solo. All of those concepts were invented to help make it easier for a project manager (or scrum master, or whoever) to keep track of and coordinate the efforts of many people on a team. Humans suck at multitasking, so, if you're solo, you shouldn't have more than one or two items in progress at a time. Meaning you shouldn't have any need for techniques that are designed to help keep track of lots of things at once.
I don't find much value in a non-paper solution because the main advantage of electronic solutions is to help with intra-team communication on a geographically distributed team. If you're an army of one, there's no intra-team communication or geographic distribution to manage in the first place.