DrayTek - Are you still searching for a VPN solution for your company? Don't want to change the existing network of the company? Why not using the "Single-Arm VPN" solution. It's quick,
DrayTek Vigor3900 Quad-WAN broadband router/VPN gateway for up to 500 simultaneous VPN connections » MNC Co., Ltd.
How to setup Site-to-Site VPN between Unifi USG and Draytek Vigor | by Heang Yuthakarn | Medium