no deposit sounds good, but I’d be more curious about the withdrawal conditions, that’s where most of these platforms reveal how “free” it really is.

I'm sure you won't be able to withdraw the coins you earn from trial mining without renting ASICs for mining. Most old devices won't pay for themselves until after the halving. It's better to spend money on buying Bitcoin now than to mine the same amount of Bitcoin, or even less, for the next two years.