@eastongage-
There is currently a DerbyTV channel on Roku but that doesn't look like the same thing. (However it seems to have problems of its own. Any program I select just goes back to channel's home screen.)
Per this Derby Nation announcement Roku removed Derby Nation on February 24, 2022.
Roku eliminated ALL channels not certified by Roku (often called "private" channels) on February 23, 2022. These were never published in the Roku channel store and could only be added by entering a code supplied by the channel developer. Earlier, in 2021, Roku discontinued its former channel development system and introduced a new system for developers to use in creating Roku channels intended for very small groups (no more than 20 users - truly "private" channels) and for channel development prior to certification.
Developers of existing uncertified channels were informed in advance of the February 2022 deadline and given six months or more to update their channel apps and get them certified. Those that opted not to do this were dropped, as warned, at the deadline.
If such a channel wishes to return to Roku, its developers need to create a version of their channel that runs on the Roku system, meet Roku's requirements for certification, and submit it to Roku.
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Ultra 4800 | Streaming Stick 4K+ 3821 | TCL Roku TV 43S245/C107X