How do you know that a firmware update is "available"?

How do you know which are applicable?

and the firmware history??
There needs to be some release notes and applicability charts somewhere.
You bring up a good point which is how do we determine if there are updates needed on our bikes.
I'm sure there are some dealers with service departments that are on top of updates because it's an important revenue source. It's those dealers that will reach out to their Alta customers and let them know there is an available update. Other dealers have service departments that are disorganized and playing catch-up with the work load, therefore their Alta customers are less likely to be informed of updates.
Perhaps Alta is aware of the disparity among the dealer base and will send out information directly to the owners, allowing the customer to drive the service request instead of the dealer. This would not be beneficial to the dealer (much better ROI when you call a customer to remind or suggest service), but it would inform the Alta owner.
In the meantime, the burden of determining if there are updates will be on the Alta service team in the form of replying to request for such info from us owners. Certainly not efficient, but hey, it's a growing company and we all expect growing pains.