The PWA ticket application uses many modern APIs, but some are not supported by older browsers. There are two browser scenarios you should be most concerned with: Internet Explorer and older Android phones. UC Browser is another popular browser that does not support all newer features yet.
Internet Explorer is the now deprecated Microsoft Browser. The only supported version is IE 11, and right now only lives on Windows 7 and in enterprises. Enterprises use many line of business applications, and many were created against old and obsolete web standards. Often, it is expensive for them to update or replace these applications.
Internet Explorer provides a legacy browser channel for them to continue running these applications. However, when they upgrade to Windows 10, they should configure these line of business applications...
