Just sharing an update (thanks for the help @Leonid S !) The issue turned out to be the Cron job trying to use an outdated version of PHP. The fix was going to cron jobs, and modifying the command to use the current PhP version (change "/local/php74/bin/" to "/local/php83/bin/").

If you find this discussion while trying to troubleshoot update issues, here is my task-list and notes for applying an update:

First, create a backup. Check PhP version, update if necessary!

Go to Una Studio/Dashboard and do a server audit. Make sure everything says OK!

If in the beta channel, the update will happen one release at a time. If in the stable channel, you are able to update from one stable release to the next stable release.

Go to direct-admin/cpanel and raise PhP limits temporarily:

• Max_execution_time
• Max_input_time
• Memory_limit
• Post_max_size
• upload_max_file_size

Click the update button, then go to file manager and public_html/logs. The log for the update (if applied) will appear in upgrade.log. When the update fails, a new log appears in sys_modules.

If the update fails, check the cron job to make sure the php matches the php version the site is using, IE:

/usr/local/php83/bin/php -q /home/(site address)/cron.php