Home Internet Port Forwarding working in 2021?

No port forwarding is definitely and issue.   I was told to add a router behind the trashcan modem.

If your not technical here are so features you might want in your router.

• Wif 6 - Wi-Fi 6 promises faster performance, better battery life for your mobile devices, and less bandwidth congestion.
• VLAN - virtual LAN is any broadcast domain that is partitioned and isolated in a computer network at the data link layer.
•  Dual Band or Tri-brand -  dual-band routers broadcast two separate signals, tri-band routers broadcast three different signals. Essentially, they're hosting three different Wi-Fi networks at once
• 802.11ac and Mu-MIMO- 802.11ac is an evolutionary improvement to 802.11n.
  One of the goals of 802.11ac is to deliver higher levels
  of performance that are commensurate with Gigabit
  Ethernet networking:  Multi-user, multiple-input, multiple-output technology
• H.323 and SIP Support - fully supports video and data conferencing.
• Wired/Wireless
• QoS - Quality of service (QoS) is the use of mechanisms or technologies that work on a network to control traffic and ensure the performance of critical applications with limited network capacity. It enables organizations to adjust their overall network traffic by prioritizing specific high-performance applications.
• Port Forwarding or Mapping:  UDP ports 5060 and 5070 to allow for full functionality for VoIP phones  

New Gateway coming in the future: Arcadyan KVD2 but port forwarding may still not be an option.