Haven't run Phex for several years... but I downloaded Phex from the link (Mediafire) in LOTR's post above, extracted, opened the .jar, installed, changed listening port to one
that I know is port forwarded within my router, connected within ~ 30 seconds. Using Windows 10 (with latest updates already installed).
Connecting as leaf, connected to 5 gtk-gnutella UPs, uptime of 5 hours or so. And successful uploads. So seems to be working fine.
In short - no problems here with Windows 10.
LOTR, I got my version from your link & not from Sourceforge