Four issues for 1.14 exist, all closed:

[x] #171
[x] #173
[x] #174
[x] #182

Other than unknown errors due to refactoring away BlockType entirely (#171), how much is left?

No idea other than custom tool damage for breaking stone. Needs testing. I track via milestones, so if you want to do that please let me know.

I.e. https://github.com/MLG-Fortress/ExtraHardMode/milestone/2