At least, you see through the network, there are WMTS calls. To get in QGIS WMTS, you need to set capabilities in the configuration
Although it works for WMTS here, it's a case by case usage.
I've added the following URL https://svc.pictometry.com/Image/BCC27E3E-766E-CE0B-7D11-AA4760AC43ED/wmts?SERVICE=WMTS&VERSION=1.0.0&REQUEST=GetTile in the datasource manager for WMS/WMTS and I'm able to add the available layers (see below)

For above layers licensing, I've followed the link in the application mentioning
Imagery - Added 2020 Imagery, for licensing questions, please click here.
The url is https://lariac-lacounty.hub.arcgis.com/pages/lariac-licensing-information-nda
To add othr layers, you can also look at https://arcgis.gis.lacounty.gov/arcgis/rest/services/DRP/GISNET_Public/MapServer and add them declaring them as "ArcGIS REST Server"