Realtime GI not working in 2019.2?

I'm trying to figure out what changed with respect to RealtimeGI between 2019.1 and 2019.2. I'm finding that nothing I do in 2019.2 gives me any indirect/realtime GI contribution, no matter what I change.

Here's a scene under 2019.1. It's a box with a spotlight in it:

5020553--491717--upload_2019-10-1_11-45-21.png

You can see the spotlight is bouncing to hit the walls and ceiling of the box. Here's the same scene in 2019.2:

5020553--491726--upload_2019-10-1_11-52-21.png

There's no contribution, regardless of what I set for Indirect Multiplier on the light itself, or the Indirect Intensity of the Lightmapping Settings.

Any other ideas on what can be adjusted to get realtime GI working under 2019.2? I know 2019.2 warns that Realtime GI is deprecated, but that doesn't mean it's obsolete/removed.

It seems that the lightmaps just aren't being baked correctly under 2019.2. If I look at the "Realtime Lightmap" previews under the 2019.1 version of this test project, it shows reasonable results:

5020565--491729--upload_2019-10-1_11-59-16.png

Doing the same under the 2019.2 version of the project shows lightmaps with just all black.empty data:

5020565--491732--upload_2019-10-1_11-59-53.png

So, this appears to be an issue where the lightmaps simply aren't baking correctly in 2019.2.

I reported this as bug #1188797. This isn't happening using the built-in renderer, so it appears to be an HDRP- (or possibly SRP-)related issue.