Apologies for the inconveniences, but older browsers may be simply not supporting features, required for TRB140 web interface.
You can at least try logging to the device via SSH and executing the following commands to download and configure DDNS service:
opkg update
opkg install tlt-ddns
Modify bolded options according to your settings and execute commands below:
uci set ddns.myddns.lookup_host='yourhost.example.com'
uci set ddns.myddns.domain='yourhost.example.com'
uci set ddns.myddns.username='your_username'
uci set ddns.myddns.password='your_password'
uci set ddns.myddns.ip_source='network'
uci set ddns.myddns.service_name='dyn.com'
uci set ddns.myddns.check_unit='minutes'
uci set ddns.myddns.force_unit='hours'
uci set ddns.myddns.ip_network='mob1s1a1_4'
uci set ddns.myddns.enabled='0'
uci set ddns.myddns.use_https='0'
uci set ddns.myddns.cacert='IGNORE'
uci set ddns.myddns.check_interval='10'
uci set ddns.myddns.force_interval='10'
uci set ddns.myddns.interface='mob1s1a1'
uci commit
/etc/init.d/ddns
For reference on configurable options, check this link.
Best regards,