There is no such device. Solar powered equipment uses a battery to buffer the supply and load. To get optimal power out of the panels you will need a charge controller between the panels and the battery. A charge controller alters the apparent voltage of the load to match the optimal voltage of the panel (which will vary depending on current conditions). Slapping a panel to a fixed 12V load is going to kill 30%+ of your output.
As for what happens if you supply a device designed to use 25 Amps less than 25 Amps? Well it depends on what undercurrent protection the device has. If it is none then it is very likely you could damage it. I would not recommend hooking a 25A device to a supply which can not consistently supply 25+ Amps.
As for ways to protect the miners, unless the miner can be throttled down to use less voltage the easiest undercurrent protection (to protect the device and battery) is to measure the voltage of the battery. As the stored energy in the battery is reduced (because device is drawing more current than the charger is supplying) its voltage will decline. When the voltage gets "too low" (which will depend on battery type and safe max discharge) the connection to the load is cut by a relay. Once the battery voltage reaches some min "cut on" voltage the connection to the to the load is restored. If there is no commercially available system that meets your needs, building one is a pretty simple electrical project.
Any reason you want to be off grid? Off grid is always more expensive. You are adding an expensive charge controller and battery to an already expensive system.
I agree , but I would like to comment that a simple charge controller does not do anything than cutting the voltage exceeding the battery's characteristics.
A simple charge controller cuts the voltage when exceeds the 13.8V (for silicone types ) and 14.2V (for Pb types).
There is nothing else it can do. It makes nothing more than what a solar panel could do directly connected to the battery (except from protecting it from overvoltage).
There is also the case of an MPPT charge controller that , as you said, can offer an additional 30% approximate gain compared to the previous case.
But such a controller would cost more than twice than what an S1 does.
Lastly, using an S1 with current lower than what needs, would create huge HW errors. No damage can be caused IMHO.