https://wiki.freshtomato.org/doku.php/wireguard_on_freshtomato
Until Wireguard is integrated into FreshTomato's web interface, it is available only via command line. However, once you understand some basic principles, configuring Wireguard is relatively simple. There are just a few caveats to be aware of. Currently, only ARM-based devices include the code needed to run Wireguard.