Hi,
I was facing this issue. Hope someone could help me.
The database has the following:
SELECT * FROM V$VERSION
BANNER
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
PL/SQL Release 11.2.0.4.0 - Production
CORE 11.2.0.4.0 Production
TNS for IBM/AIX RISC System/6000: Version 11.2.0.4.0 - Production
NLSRTL Version 11.2.0.4.0 - Production
For another part, I have the latest Visual Studio Enterprise 2017 - Version 15.9.7
When I do this simple code:

Also, when I try this way.

However, When I try to connect with the new ODP. It fails.

Also, If i try with the Visual Studio wizard is the same result.

To give extra information the versions of both DLL are:
According to dotPeek
Oracle.DataAccess, Version=2.112.1.0, Culture=neutral, PublicKeyToken=89b483f429c47342
For the other from nuget:
<package id="Oracle.ManagedDataAccess" version="18.3.0" targetFramework="net47" />
Best Regards,