OpenWrt Forum Archive
https://forum.archive.openwrt.org/viewtopic.php?id=6871728.11.2016 · If you use l2tp over internet then without additional ipsec layer communication is unencrypted. If your l2tp sever is set up to require encryption (on mac it should be easy and probably its on by default) then openwrt cant connect without additional manual configuration of strongswan. And this is not as easy as plaintext.
[OpenWrt Wiki] Libreswan L2TP/IPsec
openwrt.org › docs › guide-userSep 27, 2021 · Libreswan L2TP/IPsec. This how-to explains how to configure an openwrt router to act as an L2TP/IPsec gateway (vpn server) using xl2tpd (for L2TP) and Libreswan (for IPsec). The new strongSwan documentation is currently missing an L2TP/IPsec page. Use this one as a reference for the xl2tpd part.