Created attachment 129553 [details]
Juxtaposed displays of nm-applet (bugged) and the connection editor (correct) re. WLAN "2&6".

SUMMARY

Network connections that contain only numbers and the & character are shown in the NM applet with the "&" and any following digits cut off. The correct connection name is however shown in both nmcli and the Plasma NM connection editor.

I attached a screenshot showing the problem.

STEPS TO REPRODUCE
1. Create a connection with the name "2&2". For example, you could create a wireless network with such a SSID.
2. Open the nm-plasma popup in the panel. The connection is shown with the name "2", swallowing the "&2" suffix.
3. Cross-reference this output with nmcli output and the connection editor. There, the connection name is shown properly as "2&2"

OBSERVED RESULT

Any suffix matching &\d+ (at least, didn't test everything that's possible, including alphanumeric strings) is dropped in the NM applet popup.

EXPECTED RESULT

Every connection in the NM applet popup is shown properly, as also displayed by nmcli or the Plasma NM connection editor dialog.

SOFTWARE/OS VERSIONS

Operating System: Arch Linux
KDE Plasma Version: 5.19.1
KDE Frameworks Version: 5.71.0
Qt Version: 5.15.0
Kernel Version: 5.6.13-arch1-1
OS Type: 64-bit
Processors: 4 × Intel® Core™ i5-4210U CPU @ 1.70GHz
Memory: 7.7 GiB of RAM
Graphics Processor: Mesa DRI Intel® HD Graphics 4400

ADDITIONAL INFORMATION

This issue started to appear after installing Plasma 5.19 and/or Qt 5.15 (coming from 5.14), so this might actually be a Qt 5.15 issue or behaviour change. Unfortunately, both upgrades happened at the same time and rolling back my setup on Arch to the combination Qt 5.14 and Plasma 5.19.1 is not trivially possible, so I apologize for not bisecting.