Roy,
SBAS is only supported on certain devices, and in my experience they are very transient, appearing and then disappearing at various times. Neither the Mi 8 or the Galaxy S9 say they support SBAS, but I have a Galaxy S8+ that does occasionally show SBAS, and the S8+ doesn't officially list SBAS support either.
I'd suggest trying at different times of the day and seeing if they appear. There really isn't anything you can do to enable or disable them. On the Mi 8, though, if it's rooted and flashed with Lineage, strange things can happen, as the drivers and Android interface may not match the original device.
Sean