As long as your salary is enough to live comfortably, do what best makes sense for you. You'll probably be happier taking the path that is the most meaningful to you.

Now, personally, if you got your motivation back, I'd advise to go ahead and finish this PhD! You'll have plenty of offers in the future, probably including more meaningful ones. We are in a field where job offers are not missing. You only have one PhD (usually) and you don't want to regret having spoiled it your whole life (of course, if it is not working out, get the hell outta there). Your PhD is (supposed to be) your personal work. Your rules and your ideas. At a level your job offer probably won't reach. You'll be able to try a software developer position later, there's no rush.

(as someone who did a PhD and is now working as a software developer).

(and yes, I did decline a job offer with a much higher salary that my current one, but I'm happy to have made this call: my salary is still decent, and I do something meaningful to me, and geographically close to where my friends are)

I wish you the best. There's no wrong answer. Relax and enjoy life.