Not the only one, I'm experiencing the same problem.
There is a fix for this in the latest release (https://github.com/snozbot/fungus/releases) Fungus v3.11.3. But you have to take it from GitHub as it has not been updated in the Asset Store yet.
Fungus v3.11.4 is now available on the Asset Store and should fix the Unity 2019.1.0f2 compatiblity issues.
I tried v3.11.4 in 2019.1.0f2 and it works. Thank you so much!
I can't get the tool menu to show up in 2019.1.0f2
got it :)