Hello Fraser!
I switched back to my previous router for the time being as the internet is unusable for me on the R2.
Here is a screenshot of the QoS page. I set the Congestion Control to Never, Bandwidth Allocation to default, and turned off all Traffic Prioritization.
The R2 is plugged into a fiber Nokia modem provided by my ISP. (I'm not sure of the model number as it isn't displayed on the outside of the box anywhere.)
I am using Firefox to connect to dumaos/ and it is through HTTP.
Thank you for your assistance in this matter.