Lsusb:
Bus 001 Device 010: ID 12d1:14db HUAWEI_MOBILE HUAWEI_MOBILE
Bus 001 Device 008: ID 12d1:14dc HUAWEI_MOBILE HUAWEI_MOBILE
Bus 001 Device 004: ID 045b:0209
Bus 001 Device 005: ID 413c:81b6 Sierra Wireless, Incorporated DW5811e Snapdragon™ X7 LTE
Bus 001 Device 003: ID 045b:0209
Bus 001 Device 002: ID 2109:3431 USB2.0 Hub
Bus 001 Device 001: ID 1d6b:0002 Linux 5.4.154 xhci-hcd xHCI Host Controller
Bus 002 Device 004: ID 2001:4a00 D-Link Elec. Corp. D-Link DUB-1312
Bus 002 Device 003: ID 045b:0210
Bus 002 Device 002: ID 045b:0210
Bus 002 Device 001: ID 1d6b:0003 Linux 5.4.154 xhci-hcd xHCI Host Controller
is wrong.
Switch your modem into the composition with comm ports, switch it from Dell to Generic, update the firmware - all that has nothing to do with OpenWrt though.
Then set it to QMI mode and follow the guidelines from https://openwrt.org/docs/guide-user/network/wan/wwan/ltedongle
There're other options available as well - MBIM instead of QMI, ModemManager as a proto, etc.