Tvheadend

Once in January 2018 I asked for the feature to transcode input streams to flac.
This has been implemented (Revision a79e8292) and I used this feature on an arm board with Libreelec now for quite a while.
No I rebased my NAS to an intel board with Ubuntu 18.04.
I installed tvheadend from official repos, both stable and unstable most recent releases.
I even downloaded and compiled the source myself.
But in neither version I found, how to create transcoding to flac, although flac is enabled. The WebUI for stream config looks quite different.

What is necessary to change in the config to make flac available in the WebUI?

Thanks for your support.