It's a question I have often considered. Even though I do not consider myself to be a developer, I do write a fair amount of code. Almost all of it is for personal personal projects. I usually have 3 or 4 projects going at any given time. They progress at different rates based on available time and need. Some of my projects are just for fun so I can keep my skills current.
So do I consider myself to be an indie hacker?
It is a difficult question. I follow quite a few indie hackers or solopreneurs. I do find that there is one major difference between myself and many of the people that I follow. Most of my dev efforts are for personal interests and not economic gain. I usually have a task or goal that I want to accomplish, and that is where is focus my efforts. I am not worried about MRR at all.
For this reason alone, I do not consider myself to be an indie hacker.