In the interim, I would suggest that Ubiquiti use the Cloud Key Plus 2 to calculate speed tests, rather than the running the test on the USG. The pro models have lots of PoE, support redundant power via the USP-RPS, and have some limited L2+/L3 features like static routing and a DHCP server

Most 1st generation PoE switches have more PoE budget than the equivalent 2nd generation model. They are still a good buy if you need a lot of PoE. Their fans can get loud though. All of the Dream Machines and UniFi OS Consoles are based on modern ARM processors and Ubiquiti's new UniFi OS software platform. You can’t create custom JSON config files for them, but a limited set of manual configuration changes and Linux commands can be run via SSH, if you know what you’re doing. None of these can be adopted to an external UniFi Network controller besides the UXG-Pro.

Enterprise models have higher PoE budgets, faster interfaces such as 2.5 Gbps RJ45 Ethernet, and the features available in the Pro models This article is not applicable to the UniFi Dream Machine models, because all configurations are already available in the UniFi Network user interface. Because hardware acceleration is disabled, Ubiquiti says that enabling IPS will affect the USG’s maximum throughput:

I remember something similar a while ago when trying to adopt a USG into an existing network using a statically assigned IP raspberry pi as controller.. I changed subnets around and tried to mess with it a bunch of different ways. It DID NOT want to be adopted. Basically a UDM with an upgrade to Wi-Fi 6 on 5 GHz, two PoE ports, an SD card slot, UniFi Protect support, and 128 GB of internal storage Ubiquiti Support cannot assist in the creation of the config.gateway.json file nor will assistance be provided for command line configuration. If assistance is required, feel free to visit our Community to create a topic and ask for help with your desired configuration.Used to feed redundant DC power to the UDM-Pro, and 2nd generation Pro/Enterprise switches that support it. Not a switch, but does have an in-band Ethernet management port. The main way to differentiate UniFi switches is that the 1st generation model names begin with "US-" and the 2nd generation model names begin with "USW-". See UniFi Switches Comparison and Buyers Guide to compare all available models. New Desktop/Small Switches Features four 10 Gbps RJ45 Ethernet with PoE++ out. The Enterprise 8 PoE or Flex XG may be better options.