If they had access to them in Ukraine, both sides would already be using them I expect. Right now jamming of drones is a huge obstacle. One way it's dealt with is to run literal wired drones with massive spools of cable strung out behind them. A fully autonomous drone would be a significant advantage in this environment.

I'm not making a values judgment here, just saying that they will absolutely be used in war as soon as it's feasible to do so. The only exception I could see is if the world managed to come together and sign a treaty explicitly banning the use of autonomous weapons, but it's hard for me to see that happening in the near future.

Edit: come to think of it, you could argue a landmine is a fully autonomous weapon already.