If your Fortigate doesn't support version 5.6.1 or later, you can't manage it with a managed IP address. But you can use Fortinet Cloud to manage them.
Wi-Fi router Keenetic Hero 4G KN-2310, white
76 Review
πΆ High-Performance MikroTik hAP Mini RB931-2nD: Small 2GHz Wireless Access Point, 3x 10/100 Ethernet Ports, 650MHz CPU & RouterOS
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MikroTik RB941-2nD RouterBoard hAP Lite: Affordable 2.4GHz Home Access Point
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Mikrotik RouterBOARD 951Ui-2HnD RB951Ui-2HnD: High-Power 2.4Ghz Wireless AP with 5x10/100 Ports and OSL4
73 Review
UGREEN USB 3.0 Ethernet Adapter Hub with RJ45: Fast Gigabit Ethernet Converter, 3 Ports USB 3.0 Hub Compatible for MacBook, iMac, Surface Pro, Chromebook, Laptop, PC
11 Review
π Juiced Systems Silver BizHUB USB-C Multiport Gigabit HDMI Hub with 3 USB 3.0 Ports, Gigabit Ethernet, 4K HDMI, SD/Micro SD, and USB-C Power Delivery
11 Review
π StarTech.com NETRS232 Serial to IP Ethernet Device Server - DIN Rail Mountable - Serial Device Server - Serial Over IP Device Server (Black)
4 Review
π StarTech.com NETRS2321P: 1-Port RS232 to Ethernet IP Converter, Serial over IP Device Server - Black
5 Review