Well, I’m not sure if it’s a credible source or not. You know you can’t really trust the US Military to tell the truth these days. But here’s one link.
https://www.7atc.army.mil/JMTGU/
“Mentor and Advise Armed Forces of Ukraine Trainers: U.S. Soldiers, joined by NATO allies and partners, mentored and advised Armed Forces of Ukraine Observer Controller / Trainers at the Combat Training Center located near Yavoriv. This was accomplished by employing a “train-the-trainer” approach, enabling Ukrainians to take the lead in training rotational brigades.
“Enable Combat Training Center Capability and Capacity: U.S. Soldiers worked with Armed Forces of Ukraine partners at the Combat Training Center - Yavoriv to develop and implement systems to improve combat training and increase training center capacity. Combat Training Center - Yavoriv delivered Brigade-and-below collective training for Armed Forces of Ukraine Brigades.”
Not like this is any secret, is it?
Yavoriv is in Lviv Oblast, UKRAINE.
All that training within Ukraine was before Russia invaded, NATO was pulled out of that Ukrainian base.