core: Light group no longer shows dimmer control in 2021.5.0

The problem

I have two dimmer lights, which are both operating correctly. Both of these lights are in a group. Prior to 2021.5.0 upgrade, this group showed the dimmer control and I was able to control both lights by adjusting the dimmer control of the group. After the 2021.5.0 upgrade, this group no longer shows the dimmer control

light:
  - platform: group
    name: Bedroom lights
    entities:
      - light.dimmer_1
      - light.dimmer_2

What is version of Home Assistant Core has the issue?

core-2021.5.0

What was the last working version of Home Assistant Core?

core-2021.4.2

What type of installation are you running?

Home Assistant Core

Integration causing the issue

Light Group

Link to integration documentation on our website

https://www.home-assistant.io/integrations/light.group/

Example YAML snippet

light:
  - platform: group
    name: Bedroom lights
    entities:
      - light.dimmer_1
      - light.dimmer_2

Anything in the logs that might be useful for us?

None

Additional information