I agree, probably not optimal for multiple conversion, ethernet>optical>ethernet. Thru trial and error I found using OpticalRendu as my streamer was beneficial in a number of ways,. Firstly, Roon sound quality superior using two streamer setup, Roon core on first streamer, Endpoint on the OR which is designed for this purpose only, second benefit is the single optical conversion, third, OR optimizes usb vs what I'd get out of most streamers.
Certainly one could go optical out of router route, the issue is not all optical interfaces equal, the Sonore and other audiophile converters provide superior optical interface. I and many others have compared generic to optimized solutions, this is the general consensus.