Disclaimer: use this information at your own risk! It's not my fault if you damage something even if it's caused by explicitly following what I've shared here. This may violate your terms of service and/or warranty.
To use a Starlink User Terminal on an RV, boat or other platform where the default power-source is not alternating current in the 120+ volts range, any basic inverter will happily feed the included PoE injector and router. However, there are advantages to eliminating the components Starlink provides and switching to something like a Yaosheng injector with a router of your choosing (or even no router at all). This article describes roughly how I did this on our 12-volt based sailboat.
Note: At the time of this writing there are a handful of user terminals in existence including Gen 1, Gen 2, Gen 3, and High Performance. This write-up is based on the High Performance terminal but have done the same conversion on a Gen 2 and believe it would also work for Gen 1 as well. I have no experience with Gen 3.
While this modification does take a bit less power than the Starlink-provided PoE injector and router, the energy savings is pretty minor and actually not really on the list of reasons for my decision to implement it.
For me, the primary purpose is to simplify the components required for our boat to have an Internet uplink via Starlink. Inverters are relatively complicated and noisy (RF-wise) devices in comparison. We depend on the Internet to monitor our systems and, when something is going wrong with our power supply, the inverter is often the first thing to go. Also, there are times when it is helpful to shutdown the inverter to minimize RF noise while working the HF radio, or to conserver power if we're getting into a tight spot. I prefer to be able to do this without losing Internet connectivity.
The other reason is that I want to use my own router. Sure, I could just plug the Linksys into the Starlink router, but this introduces another NAT layer and leaves completely unnecessary component involved. I run OpenWRT on the Linksys which enables a large number of capabilities that the Starlink router does not including things like local DNS, Multi-WAN load balancing, and reverse-tunnel VPNs.
For whatever reason, the first time I hooked everything up, the Starlink powered on and my ethernet negotiation light on the router would briefly come on, but would quickly go off and there was no connectivity. I could tell the terminal had power because Starlink showed it as healthy in their app (via other Internet access). I re-terminated the cable and everything then worked fine.
The LAN connection on the PoE injector is essentially equivalent to the ethernet connection provided on a cable modem, DSL terminal, etc. Just configure the router as you would for anything else and you should have internet within a few minutes of hooking it all together. You could even just plug your computer directly into the LAN port without any router!
I never measured the power consumption of the Starlink-provided PoE injector and router before giving them away so can't say how much power this conversion saves. Starlink power terminals vary in what they draw depending on what they're doing (heat, searching, firmware updates, etc.) but my HP generally draws something like 2 amps at 12 volts including the booster and injector. The Linksys router's consumption is basically unnoticable.
Here is a video of a cheap ammeter between the breaker and the booster showing an example of the terminal's startup to stabilization.