Yes. The 100.aaa.bbb.ccc (obfuscated) IP address is indicating that your ISP is using CG-NAT since addresses in the range 100.64.0.0 to 100.127.255.255 are reserved for CG-NAT.
Unless you talk to your ISP, your only solution is to use Tailscale.
UPnP will not work with multiple nat layers no matter whether that is due to multiple routers or a CG-NAT service provision.