I just updated my Mojave machine to Security Update 2020-006 but my bridgeOS has not updated, it remains on 18P50347c which I got when I tried Big Sur DP4/PB1 on 7 August 2020?

I don't have any other Macs so "downgrading (from beta to release) bridgeOS using Apple Configurator 2" isn't an option.

How can I get the latest bridgeOS on my Mojave Mac mini?