Hey @Hopper,
I would like to help you as much as I can with your request because, as you can see, I was involved in the pull request, which you referenced.
The transmission 4.0.x version is available within OpenWrt 23.05 (not released, yet) and the master branch.
What could be possible is that someone is willing to look at it and bring it by backporting it (It means - compile it, run testing, make sure that it does not break anything - you make sure about backward compatibility) and if you are sure that everything goes alright. It does not bring any build failures to other packages as it might require some other packages to be updated as well, then send pull request to OpenWrt packages repository. I will happily merge it if is alright.
Also, in my opinion, it is better to cooperate with OpenWrt repositories as it will also be included in Turris OS afterward as they are following their latest changes in relevant branches instead of having it only in Turris OS, because it will end up with the same situation as it happened in the past with 3.x version. It’s preferred if everyone can benefit from it.
Maybe Turris guys will look into it. We will see.