Tire load inflation is provided by each tire manufacturer. They are then sent to the TRA for standardization. Tire brands are not a consideration factor.
All ST/LT tires conform by size designation to
load range inflation charts. Load index numbers on ST/LT tires are strictly for the addition of tire speed letters following the load index number. Example: The ST235/80R16 LRG has a load index number 129L. The "L" is it's speed rating letter equal to 75 MPH.
Here are a couple of load inflation charts for RV trailer tires. The first one is from GY and includes all tires they approve for RV/RV trailer service.
https://www.goodyearrvtires.com/pdfs/rv_inflation.pdf
This second chart is from Sailun and includes all tires they approve for RV trailer service.
https://fifthwheelst.com/documents/C...T-Modified.pdf
For all other PSI to load inflation, I have found the Toyo tire chart to be the most comprehensive. It's probably most useful for installers of replacement LT tires for OE Passenger/Euro metric tires.
https://www.toyotires.com/media/2125...s_20170203.pdf