I remember that there should be a test Depot in the backend of Steamworks, but I forgot where to set it up. 0.49.1 version can be downloaded at the following URL
By the way, I recently updated the Steamworks plugin in itch and added the AutoBuildTool easy deployment tool, you can try to use it to see, if you still don't understand, you can find me at the following official Discord of RPG Maker or SigmaSuccour's Discord, I found it in my name of the Discord is"Mirai"
RPG Maker - Discord
SigmaSuccour - Discord
(by DeepL Translator🙇♂️)