MAX BRI Mini "Use Both SIMs" setting

Does anyone know exactly what this does? I have SIM’s for two different carriers installed (both active accounts). What does selecting this setting actually do if there is only one cellular radio?

Welcome to the forum.

The BR1 Mini will failover from SIM A to SIM B when SIM A fails (and vice versa).
If you select SIM A only (or SIM B only) it won’t failover to the other SIM.

Does failure mean failing configured Health Check or the SIM is corrupt and can’t be read?

The BR1 will failover to the other SIM when there is no working internet connection.
This could be because of a failed heath check or because of a SIM that is corrupt or out of data.
You could also configure a cellular signal threshold to force a failover when a cellular signal is below a certain value as explained in the video below.

Someone else raised a similar question in this post. @SteveTaylor replied to that question with a few more useful details.