Craft updater still spinning after at least half an hour--no error message I hadn't updated site in a while now. Checked Craft's control panel and something like 12 updates were available and i clicked update. "Updating Composer dependencies (this may take a minute)…" has been on display for over half an hour, maybe an hour, and the activity spinner just keeps spinning. No error report or any feedback. I'm reluctant to stop the process as the site is currently unavailable due to this situation.
If you have ssh access to your remote server you might be better off just updating composer via command line. I find it's ofter faster and less prone to causing errors by updating composer and craft this way.

Let me know if you need help doing that.