SUMMARY
Basically, if one connects to a Wi-Fi hotspot with 'Limited/No Internet Access', Plasma's UI freezes anywhere between 8 - 15 seconds, until it actually reflects that information on the widget. It seems like while Plasma's 'Frozen', NM or the widget is figuring out whether the connection has Internet.


STEPS TO REPRODUCE
1. Connect to hot-spot without Internet Access or with DNS issues.
2. Try interacting with Plasmashell, while the Network Widget is testing the connection.

OBSERVED RESULT
Plasmashell freezes for a couple seconds, while the Network Manager figures out Internet Availability.

EXPECTED RESULT
Plasmashell doesn't freeze during the check.

SOFTWARE/OS VERSIONS
Operating System: openSUSE Leap 15.4
KDE Plasma Version: 5.25.4
KDE Frameworks Version: 5.96.0
Qt Version: 5.15.5
Kernel Version: 5.14.21-150400.24.11-default (64-bit)
Graphics Platform: X11
Processors: 4 × Intel® Core™ i5-3320M CPU @ 2.60GHz
Memory: 7.6 GiB of RAM
Graphics Processor: Mesa DRI Intel® HD Graphics 4000
Manufacturer: LENOVO
Product Name: 2347G2U
System Version: ThinkPad T430


ADDITIONAL INFORMATION
Granted, this scenario is quite niche. I'm just mentioning it for the sake of polish (if any is required).