Winter '22 changed Salesforce app's default behavior

 Winter '22 has changed the Salesforce mobile app's default behavior, but not exactly how you'd gather from reading the Release Notes, which states
"The Salesforce mobile app now selects the first available Lightning app by default—instead of Mobile Only—which results in a change to the app’s bottom navigation bar. Users who don’t have access to any phone-activated Lightning apps still default to Mobile Only."

Granted, I didn't read the Release Notes, but even if I had, that wouldn't have been what I expect to happen once Winter '22 hit and I opened the Salesforce app for the first time.  This is what greeted me:
"You don't have access to any apps.  Your admin can help with that."

 

The mobile app was happily showing me recent records and other goodies as you'd expect from a default mobile setup.  After it donned on me that Winter '22 just hit the night before, some searching around landed me on the language in the Release Notes, but no matter how I read it, I understand it as that if I had no mobile (phone) enabled Lightning App (which is the situation with the test org), the mobile experience wouldn't have changed, because it should have still loaded the Mobile Only navigation.  And Mobile Only hasn't been disabled as far as I can tell (documentation about it is also confusing as hell), which is something else that could cause this weird No Objects screen (reported as a Known Issue).

After figuring it out (hopefully that's all of it), I went ahead and enabled one of the Lightning App.  I cleared the cache and restarted the app, and the familiar UI is back.  Sigh of relief...

Update 10/11/21: the problem happened one more time.  After checking all the settings to be fine, I cleared the app cache again, and it started working.  Feels like there's some internal flakiness to the app...