I'm also on RPi4.
What version of LE were you on before you upgraded the nightly and broke Transmission?
I can't help much more. I would suggest you install the broken Transmission from Thoradia to get all the dependencies, then install this over top of the version that it provides.
I started with a working version, then upgraded the nightly which caused Transmission to stop working. I rebuilt it and installed that, then it started working again.
Just one clarification that this is for RPi4 only.