Britain's estimate indicates that approximately 450,000 russian military personnel have been killed or wounded.
When questioned about russian losses, Minister of State for the Armed Forces Leo Docherty stated, "Our estimation suggests that around 450,000 russian military personnel have been killed or wounded, and tens of thousands have already deserted since the conflict began."
Not all lessons from Ukraine will apply to NATO militaries, but this is one that will.
Russian Orlan ISR UAVs are not very sophisticated but they are cheap and easy to produce. That means Russia produces them in large numbers and they are expendable.
But many of the current countermeasures are more expensive and scarcer. So Ukraine generally can't launch SHORAD or MANPADS to shoot them down, giving Russia persistent ISR coverage behind Ukrainian lines.
MANPADS also are not optimized for defeating them. Developing cost-effective countermeasures should be a priority.