Boards and circuitry will be fine. That fluid has been used used in many makes of HV power supplies for decades and I've never seen any issues from using it.

20-25C will actually probably be too cold and the miners will not be happy until the chips get warmer. Again, you will want to look at reported chip temps - not the 'air' temp in and out. With immersion cooling the chips run much closer to fluid temp because heat transfer between the chips and fluid is much higher as opposed to air cooling where chip temps are much higher than the cooling air.