AndrewZ

Many thanks for all the suggestions. I already found RonR's script on DSLR and going to give it a try. I'm aware of Incredible... and I'm not going to install it, I share most of the points already mentioned. Many thanks for all the answers. Raspbx did a very good job for me (respect to Gernot!) but after a few reinstallations over past years I simply need something different.

can you suggest any good alternative?

Many thanks. Just completed the upgrade from 14 to 15 on my old system. Fortunately I have a spare RPi, so will try to make a clean install there and then play with the backup/restore.

Do you think it will be possible to backup/restore the database and configs between the old and new systems? I would prefer to avoid recreating everything - extensions, trunks, routes, etc.

Just follow Asterisk documentation to configure SIP-over-TLS.

If SPA is local to your server then you probably don't need authentication and registration....

Forget about Asterisk for a while, check dmesg for modem and port related messages,...

We're using Huawei E171 & E173 dongles.