I am using same configuration files for OpenVPN, same operating system (ubuntu 20) on two different laptops, but I notice with Wireshark, then on one of them, the VPN connection goes through UDP, including all DNS requests, so I don't see any DNS, but the other laptop, all through TCP, and I see the DNS requests. One of the differences I noticed between the outputs on the command prompt of the OpenVPN process, was the network interface on the laptop that did not send DNS through tunnel was IFACE=wlo1, the other was IFACE=wlp2s0. They both had similar output here:
/etc/openvpn/update-resolv-conf tun0 1500 1553 172.16.xx.xx 172.16.xx.xx init dhcp-option DNS 172.16.xx.xx
Why is DNS not going through tunnel, and why is it using TCP? Config files are same.