Look, I use linux too, but unless the developer refuses to provide any support at all and is outright hostile, there's really no need for that tone in a comment, there are ways to provide feedback without sounding this dismissive of others people work, specially in smaller projects like this, only so much one can fix and test you know.
You are right, my tone was harsh. I edited my comment.
You have to keep in mind that when I wrote that comment, I just had spent 5$ on this tasks organizer that advertised itself as having Linux support and that ended up not working, while, for example, Getting Things GNOME not only works flawlessly on Linux, but is it also free of price and free as in freedom. I felt a little scammed, and I did not want someone else to buy it and be in my situation until the devs fixes it. (Last time the devs updated this is back in 2021 btw)
But you are right, it should not have influenced my tone, and I'm sorry to the devs and anyone else I offended.