In BC 14.10 (CU 09 Dynamics 365 Business Central Spring 19 Update W1)
I'm trying to use DotNet to access an external DB
At the first step to use DotNet, we neet to add { "target": "OnPrem" } setting into the app.json,
but I receive the error like below.

(Same setting at extension 4.0 (BC15) is ok)
Is that mean, in extension 3.0 (BC14) can not use DotNet assembly now ?