Both Poland and Romania operate F-16’s.
So “near Ukraine” is not a problem. If a Ukrainian F16 needs more intensive service it’s not far away.
And the real issue with service isn’t parts or equipment, which can be bought or donated, it is personnel. And Europe is full of experienced F16 maintainers that could easily be hired to work in western Ukraine and besides servicing F-16s, do a train the trainers thing with the Ukrainian AF crews.
Nevermind.