My introduction to hydraulic repairs was 9 or 10 years ago when I bought a backhoe that was "READY TO WORK". It showed up with one stabilizer squirting fluid 20 feet out when it was moved. I had done a little research and had read the New Holland recommended fluid was their 134D spec at the time. It might not have mattered in the hydraulic system but they recommended it in everything including trans and rear axle.
SOOO not knowing better I drove an hour and a half to the nearest NH dealer and paid too much for a kit and some fluid. The guy sold me 303 and said that was what it needed. On the way home I got to thinking about it and pulled in a Tractor Supply. After looking over all their labels I saw their Premium Travelers listed the NH134D spec so I bought some of that.
Several cylinder repairs and fluid changes later I ended up using that in everything on the NH and have even poured it in my JD 4310 eHydro trans with no ill effects so I have stuck with that.
On the Kubota I used their Super UDT2 since it's under warranty. I recently looked at this
Triax stuff that gets good reviews and I might change to that at some point. Some reviews claimed it lessened the hydro whine. Others like that it had the red dye in it and was easier to see on the stick.