Q:

Are external objects only available via Lightning Connect now?

I dabbled around with External Data Sources a while back with this public Northwind OData data feed. I decided to take another look at it for a project we are working on, but it appears Salesforce has changed this feature so it no longer works with OData and external objects. The documentation now talks more about Files Connect and Lightning Connect, and doesn't say much of anything at all on how to use a Simple URL to connect to an external OData data source for defining External Objects.
When I look at the screen, the page still makes mention of connecting to third-party databases and content systems:

Has Salesforce removed the ability to connect to an OData Data Source using the out-of-the-box External Data Source feature?

A:

Simple URL is used for Files Connect and is not related to what was called Lightning Connect (now called Salesforce Connect).
As for whether Salesforce removed or crippled the feature, the answer is no.  Salesforce Connect has ALWAYS been a paid add on.  It is available for free on Developer Edition orgs to try out and see if it suits your needs, so maybe that's where you used it. 

