You could do the preparations before a new boot so the full progress is shown in the logs.
Personally I’d recommend adding a new journald configuration to not to do rate limiting but this is not absolutely necessary. This can be done by
mkdir -p /etc/systemd/journald.conf.d/
cat <<EOF >/etc/systemd/journald.conf.d/debug.conf
[Journal]
Storage=persistent
RateLimitIntervalSec=0s
RateLimitBurst=0
SystemMaxUse=100M
RuntimeMaxUse=2M
EOF
And then add the sysconf args for ConnMan (since this works, I guess clat.c and nat.c from the 1st post suffice):
cat <<EOF >/etc/sysconfig/connman
SYSCONF_ARGS=-d plugins/clat.c -d src/nat.c
EOF
Changes will be effective after the services are restarted or the device is rebooted.
The resulting archive can be then sent to connman-debug@jolla.com
After taking the logs you can just simply remove the created files.
rm /etc/systemd/journald.conf.d/debug.conf
rm /etc/sysconfig/connman