Arch Linux

@esrevinu did adding that option make a difference for you if you build the package locally?
By default the option should be enabled when not specified see https://gitlab.freedesktop.org/NetworkManager/NetworkManager/blob/f51eee3aeff7ac3373c50767b5dfb552a8dd4268/meson_options.txt#L35

I tried building the package with that option '-Dmodem_manager=true', but the issue was not fixed.

I built 1.4.2 with the previous PKGBUILD using the classical build system. The issue was gone.

If I replace /usr/lib/NetworkManager/1.14.2-1/libnm-device-plugin-wwan.so with a working one, the issue is fixed.
It seems that meson does not link libraries correctly.

❯ ldd good/usr/lib/NetworkManager/1.14.2-1/libnm-device-plugin-wwan.so
linux-vdso.so.1 (0x00007ffc83500000)
libnm-wwan.so => /usr/lib/NetworkManager/1.14.2-1/libnm-wwan.so (0x00007f7082d3a000)
libgio-2.0.so.0 => /usr/lib/libgio-2.0.so.0 (0x00007f7082b2f000)
libgobject-2.0.so.0 => /usr/lib/libgobject-2.0.so.0 (0x00007f7082ad9000)
libglib-2.0.so.0 => /usr/lib/libglib-2.0.so.0 (0x00007f70829b7000)
libpthread.so.0 => /usr/lib/libpthread.so.0 (0x00007f7082996000)
libc.so.6 => /usr/lib/libc.so.6 (0x00007f70827d2000)
libsystemd.so.0 => /usr/lib/libsystemd.so.0 (0x00007f7082744000)
libmm-glib.so.0 => /usr/lib/libmm-glib.so.0 (0x00007f7082673000)
libgmodule-2.0.so.0 => /usr/lib/libgmodule-2.0.so.0 (0x00007f708266d000)
libz.so.1 => /usr/lib/libz.so.1 (0x00007f7082456000)
libmount.so.1 => /usr/lib/libmount.so.1 (0x00007f70821fd000)
libresolv.so.2 => /usr/lib/libresolv.so.2 (0x00007f70821e4000)
libffi.so.6 => /usr/lib/libffi.so.6 (0x00007f7081fd9000)
libpcre.so.1 => /usr/lib/libpcre.so.1 (0x00007f7081d67000)
/usr/lib64/ld-linux-x86-64.so.2 (0x00007f7082d5b000)
librt.so.1 => /usr/lib/librt.so.1 (0x00007f7081d5d000)
liblzma.so.5 => /usr/lib/liblzma.so.5 (0x00007f7081b37000)
liblz4.so.1 => /usr/lib/liblz4.so.1 (0x00007f7081b18000)
libgcrypt.so.20 => /usr/lib/libgcrypt.so.20 (0x00007f70817fc000)
libdl.so.2 => /usr/lib/libdl.so.2 (0x00007f70817f5000)
libblkid.so.1 => /usr/lib/libblkid.so.1 (0x00007f70815a4000)
libuuid.so.1 => /usr/lib/libuuid.so.1 (0x00007f708139d000)
libgpg-error.so.0 => /usr/lib/libgpg-error.so.0 (0x00007f708117d000)

❯ ldd bad/usr/lib/NetworkManager/1.14.2-1/libnm-device-plugin-wwan.so
linux-vdso.so.1 (0x00007ffe7ad2e000)
libnm-wwan.so => not found
libgio-2.0.so.0 => /usr/lib/libgio-2.0.so.0 (0x00007fd404e44000)
libgobject-2.0.so.0 => /usr/lib/libgobject-2.0.so.0 (0x00007fd404dee000)
libglib-2.0.so.0 => /usr/lib/libglib-2.0.so.0 (0x00007fd404ccc000)
libpthread.so.0 => /usr/lib/libpthread.so.0 (0x00007fd404cab000)
libc.so.6 => /usr/lib/libc.so.6 (0x00007fd404ae7000)
libgmodule-2.0.so.0 => /usr/lib/libgmodule-2.0.so.0 (0x00007fd404adf000)
libz.so.1 => /usr/lib/libz.so.1 (0x00007fd4048c8000)
libmount.so.1 => /usr/lib/libmount.so.1 (0x00007fd40466f000)
libresolv.so.2 => /usr/lib/libresolv.so.2 (0x00007fd404656000)
libffi.so.6 => /usr/lib/libffi.so.6 (0x00007fd40444d000)
libpcre.so.1 => /usr/lib/libpcre.so.1 (0x00007fd4041db000)
/usr/lib64/ld-linux-x86-64.so.2 (0x00007fd40505a000)
libdl.so.2 => /usr/lib/libdl.so.2 (0x00007fd4041d4000)
libblkid.so.1 => /usr/lib/libblkid.so.1 (0x00007fd403f83000)
libuuid.so.1 => /usr/lib/libuuid.so.1 (0x00007fd403d7c000)
librt.so.1 => /usr/lib/librt.so.1 (0x00007fd403d72000)

Setting RPATH for libnm-device-plugin-wwan.so and libnm-device-plugin-bluetooth.so, I can fix the issue.