I mean what metric would we even use? Equipment level? Quality? I reckon it won't (or shouldn't) be profit since every miner out there is for profit.
I'd honestly just compare it to how people compare pc builders. You know someone does it seriously if they've built/customized something heavily and are always using the latest rigs/maximizing literally every part they have regardless of how good it is. I'd probably use the same here with miners, just a comparison between the quality of equipment, optimizations, etc.
I'd probably consider one a "hobby" miner if they just fired up a random rig they found in their garage and just mined whatever really. Like they probably just got the bare minimum they could needed to start mining.
Not everyone is out there for profit. That's the point.
I personally feel I have drifted into the hobby miner status for what I feel it is. There is no possibility of the hardware I have ever generating a profit. But, I do love tinkering with it. Attempting to fix broken miners that I just about have 0% chance of fixing. See how quiet I can make an old miner so I can use it as a space heater and so on. People have called me a home miner. But, to me a home miner is still someone trying to make a profit mining at home or the office or wherever but it's not their main thing.
Instead of home miner should it be small miner?
All in all it's not THAT important but at times I have seen someone say home miner, when it looked to me to be more of a hobby because they knew that even with $0.04 kwh electric that the miner they bought would never make a profit. But it was fun to play with.
The GPU rig that just I put together for running vanity search was never going to make me a dollar, but it was fun until the smoke came out.
-Dave