Recommended way to define scan intervals for sensors?

Configuration
2

Disable polling on the integration in the UI. Then use homeassistant.update_entity at whatever frequency you want via an automation.

- alias: 300 Second Polling
  trigger:
  - platform: time_pattern
    minutes: "/5"
  action:
  - service: homeassistant.update_entity
    target:
      entity_id: ... insert entity id here ...