Yes agrea, the Port Scan is powerfull because i know how to use Nmap and iḿ the rare gui who know the QLineEdit can be use as normal like CLI.
I have show the Network Utility to other Dev and each time my use of the LineEdit is a surprise. Power full but totally un commun....

The Network Utility have been fast to devellop because the backend was out of the scope. All my work consit to use nmap over a QProcess and speck with it over signals.

Sorry for the next part. My job daily job is arround Network .

The MAC reverse lookup is call OUI protocol (https://en.wikipedia.org/wiki/Organizationally_unique_identifier)

In fact we have to integrate all they contructor list:
http://standards-oui.ieee.org/oui/oui.txt
http://standards-oui.ieee.org/oui28/mam.txt
http://standards-oui.ieee.org/oui36/oui36.txt
http://standards-oui.ieee.org/iab/iab.txt

Greate a big dataset , and make a search inside ....
Some Python module all ready make it job...

I really not want to creat from scratch a Scanner Backend, especially because it have to be maintain over the time.

I totaly understand you need, in general i go to my DHCP lease in that case, but you speack about a user story where the user can be in front of a Unversal Discover Tool.

The propose of Network Utility is network troubleshooting clearly not a unversal network discover.

That type of technology is totaly not the original approch of nmap.
In general a discover is base on Multicast and Broadcast , where nmap (at first) scan host by host , that nean Unicast.

Look a implementation:
https://github.com/julienblitte/UniversalScanner
https://www.microfocus.com/en-us/products/configuration-management-system-database/overview

The original issue #112 just speack about a nmap GUI. Then by design, when i have think about the Network Utility, i have focus to let nmap (and other tools) make they work.

A Universal Discovers System is really special it couple UPNP, Bonjour, ZeroConf, Scan Unicast , Scan Group Multicast, Zigbee, Bluetooth LE, Z-Wave, LoRa and more if needed .... It type of scanner is common IoT

You can do the search by you self Port Scan is just a micro part of the job.
https://arxiv.org/abs/2204.02538

Summry:
I undestand you user storie, i really understand... but to me it look like 10 years full time job, i can confirme to you.
I havent the time to create a Universal Network Discovery, and just the idea to maintain it over the time stop me in place.

My job is just base on the #112.
the code is OpenSource (And i'll help you), you can make a try ...