[BUG] DNx Codecs No Longer Supported?
ISSUE: As of v18.4, DNx Codecs no longer work properly in AE (as well as Media Encoder and possibly others). For example, a known good (works in other programs, as well as older versions of AE) DNxHR HQ video with Alpha will appear completely black.
REPRODUCTION: Import a DNx video file, for example DNxHR HQ with alpha channel into After Effects.
WORKAROUND: Rolling back to v18.2.1 works as a workaround, but is not viable long-term or with remote teams.
SYSTEM INFO: This issue has occurred on various Windows-based machines of various capabilities. Some of the editors on my team who have reported the issue to me may be working on a Mac, but I am not sure.
SUGGESTED FIX: See what changed in regards to DNx codecs from v18.2 to v18.4, restore DNx codec support in next After Effects update. Look into issues with Media Encoder and other applications as well.

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Bryan Fugal commented
Same problem receiving DNx assets from Davinci on a PC to Adobe suite on a Mac. No support in Premiere, Media Encoder, or After Effects
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Antoine Autokroma.com (Independent Developer of AfterCodecs, BRAW Studio, PlumePack, Influx) commented
Do you confirm you are on Windows to test this ? What about After Effects 2022 BETA ?