At OsmoDevCon 2024, @fixeria and roox managed to set up and demo transmitting Telefax over GSM 9600 bps Transparent Circuit Switched Data, using a network consisting only of Osmocom components: osmo-{trx,bts,bsc,msc,hlr,mgw,stp}.
The two fax machines were Possio Greta devices broght by @laforge.
There was quite a bit of late-night debugging required at the previous night, as far as I heard mostly some bearer capability problems in osmo-msc. I hope we’ll see the patches in gerrit soon.
Thanks to @Manawyrm we have a video recording at https://www.youtube.com/watch?v=rfDxGZlmnH4 (interesting bits mostly toward the end).