I am looking for a router with a built-in 3G/LTE modem, 4 Ethernet ports, WiFi and a USB socket (ver 2 is enough). I searched and there are many such routers but without a USB port. Maybe someone knows the model of such a router with USB, working under Open WRT?
ZBT WE-826 has required features.
I believe these searches are a bit misleading. There are many other options, but most of them are not matching the "LTE" modem search because the internal modem is optional.
Looking at the range of ZBT routers known to support LTE modems, like the one @reinerotto points to, I see that they most of them specify the modem slot as "1 x miniPCIe". Which is technically correct, but somewhat incomplete. The important part is that they have a miniPCIe slot with USB2 and SIM connections, allowing you to use whatever miniPCIe LTE modem you want.
This includes a number of alternatives with a more powerful MT7621 SoC, with gigabit ethernet ports if that is of interest.
There are also boards with m.2 slots supporting LTE modems (having SIM, USB2, USB3 and "B" key), like the WPJ428, without any indication of this at all in the hardware table.
So I believe the question is fair, and pointing to the hardware table is not an answer.
Note that I am not complaining about the hardware table. It's a great information source and extremely useful for narrowing down the search or verifying OpenWrt support for potentioncal candidates. But it will probably never be complete enough to allow searching for more obscure features like LTE support. If you want that, then we need a separate "eSIM/SIM slot(s)" column. That's the main hardware indicator of internal 3G/LTE/5G support.
So looks like to use for example any TP-Link or D-Link with USB port and connect for example Huawei USB LTE module, with SIM and SD card socket build in.
Huawei 4G Router with Bridge Mode? -->Openwrt?
No. I need router because ob port redirection to LAN IP.