Unexpected FLV instead of H264 on 1.10.11/Debian12

We have been running 1.10.10/Debian11 with no problems, but when we tried 1.10.11/Debian12 the video codec was unexpectedly FLV instead of H.264.

We’re going to partially revert to 1.10.11/Debian11 but we’d like to know if there’s a solution for Debian12.

What are the steps to replicate this? More information is needed please.