Does the HORIZON 30 Series support HDR10?

Yes.
The HORIZON 30 Series supports HDR10 content.
Check whether HDR10 is active
1. Play HDR10 content.
2. Press the Settings button on the remote to open Quick Settings, then select Display.
3. Check Picture Mode. When HDR10 is active, the picture mode name displays "Picture Mode(HDR10)".

Note
- HDR is enabled by default.
- If HDR10 content is playing but (HDR10) is not displayed, go to Display → Advanced Settings and make sure HDR is turned On.