I finally managed to get Jigasi to connect to my 3CX and to actually dial into a Jitsi conference.
However, the next problem I ran into is that while on the phone I can hear what is said in the Jitsi conference, the same is not true vice versa: What is said on the phone can’t be heard in the Jitsi conference.
Once the call is established, I see the following error messages from Jigasi:
Jigasi 2021-07-17 05:28:23.377 SEVERE:  net.sf.fmj.media.Log.error() Unable to handle format: LINEAR, 48000.0 Hz, 16-bit, Mono, LittleEndian, Signed Jigasi 2021-07-17 05:28:23.384 SEVERE:  net.sf.fmj.media.Log.error() Failed to prefetch: net.sf.fmj.media.ProcessEngine@5e788691 Jigasi 2021-07-17 05:28:23.390 SEVERE:  net.sf.fmj.media.Log.error() Error: Unable to prefetch net.sf.fmj.media.ProcessEngine@5e788691 Jigasi 2021-07-17 05:28:24.386 SEVERE:  org.jitsi.jigasi.SipGatewaySession.run().1534 [ctx=162649969967438172529] Stopped receiving RTP for Call: id=1626499699619146676737 peers=1
In case this matters, at this point in time, the incoming call is just from another internal extension (I will try external calls, once the internal ones work).
Any experience with this error (I found topics where people had the one way audio problem but in the other direction)?