How to construct Gstreamer pipeline as HLS packager from MP3 sources?

Question

I'm looking into the simple use case of transcoding a MP3 source to a HLS manifest file. Audio only, no video involved. My test have been using a local MP3 file as source, but unsuccesful.

Ultimately, what I'm looking for is to, based on source stream detected ad signals, make the HLS packager inject custom HLS tags and discontinuity tags, accordingly and as precise as possible. Said source streams are live MP3 sources. If you've got suggestions for solutions already doing this, please let me know. The working idea is that Gstreamer would be a good choice because is possible to inject discontinuity tags via an API once ads are detected. Ffmpeg does not allow this.

Here is the command I'm using:

sudo GST_DEBUG=3 gst-launch-1.0 filesrc location=./test.mp3 ! decodebin ! audioconvert ! avenc_aac ! queue ! mpegtsmux ! hlssink max-files=5 target-duration=3 playlist-location=playlist.m3u8 location=segment%05d.ts

The resulting manifest is 1 segment only with size equal to the whole file duration. That is not the expected result having segment sizes of 3 (target-duration)