Apps similar to icmptx include Iodine, which is free and open source. Other options are DNScapy and SlowDNS. In total there are three VPN Services like icmptx for Mac, Windows, Linux, Android and self-hosting.
iodine is a free (ISC licensed) tunnel application to forward IPv4 traffic through DNS servers (IP over DNS). Works on Linux, FreeBSD, NetBSD, OpenBSD, Mac OS X and Windows.
DNScapy is a DNS tunneling tool. The code is very light and written in Python. It includes a server and a client. The server can handle multiple clients.
