It varies from person to person, and from horn to horn. The fingerings I use on my Prestige are different from my old Boosey and Hawkes.
Currently, I have found these fingerings to work best for me:
B: 2 + tuning trigger
C: 1-3
C#/Db: 2
D: 2 + tuning trigger
D#/Eb: 1
E: 2
F: open OR 4 (depending on context)
B is a tricky note to hit for everyone. It takes a lot of practice and focus to really center it. Once you work up the the high D/Eb range, though, it gets easier. I also use 2 for both Db and D, which might sound a bit weird, but those notes seem to respond best with that fingering. Open on D is too hard to center, and 2-3 on Db is too tubby.
It's best to experiment around and find what works best for you.
University of Miami - BM Euphonium Performance '21
Indiana University - MM Bass Trombone and Euphonium Performance '24
Besson Prestige 2052S
Courtois 551BHRA
Conn 88HCLSGX
Various Greg Black mouthpieces