URL Previews not working for e2e rooms, even with previews enabled

**Describe the bug**
With the introduction of url previews in 1.0.12, we now have parity with Element web, except for e2e rooms. I'm a member of a large number of e2e rooms with URL previews enabled (in element web) that are not expanding in element android.

(This used to work with the old version of riot-android, fwiw.)

**To Reproduce**
Steps to reproduce the behavior:
1. Create and enter an e2e room.
2. In Element web, go to room settings -> General -> URL Previews, and "enable URL previews for this room".
3. Post a URL in the room, watch as it unfurls in Element web.
4. Open the room in Element android, watch as it shows a bare URL with no preview.

**Expected behavior**
I was expecting a preview. :)

**Smartphone (please complete the following information):**
- Device: Samsung Galaxy S7
- OS: Android 10 (LineageOS + microg)

**Additional context**
- 1.0.12 - Google Play Store
- Homeserver: private synapse instance