I could never force OpenVPN to use the remote DNS provided by the vpn server in the latest Raspberry Pi OS (ubuntu has no problem in network manager by default). I've tried so many ways to fix the DNS leak in Raspberry OS following the tutorials online and nearly all suggested a public DNS such as 22.214.171.124 and 126.96.36.199 through settings in Router or .conf. Even though I could force the DNS to 188.8.131.52 or 184.108.40.206 etc. it still leaks my country of origin because Google/etc. forwards the requests to a local DNS server with a local IP.