Rockbox unfortunately is built with "dinosaurs" in mind. As a side effect, the project does not intend to properly handle modern ID3, Vorbis tags.
I could use an older Android phone, but would have to find a suitable device to de-Google and load a custom music player app onto (such as Vinyl). Neither my Pixel XL nor Pixel 5a that I own currently are suitable targets (neither have microSD support, my Pixel XL has a damaged headphone jack and needs to be repaired). If you have any recommendations for something used that has a headphone jack, microSD slot, and can bootloader unlock via adb, let me know.
The explicit denial I saw is multi-genre, multi-artist in ID3 v2.4 I won't be parsed.
EDIT: The source.
Rockbox will only pick up one of a tag (RIP Vorbis) and will only parse up to 500 bytes on higher end players, 240 bytes on other players of the grouped tag (RIP ID3 v2.4).