Can someone suggest a device which is able to work with SIM card, can be powered from microUSB/type-c 5V power supply and openwrt can be installed on it?
Something like Mikrotik mAp lite (https://mikrotik.com/product/RBmAPL-2nD) but with LTE support.
gl.inet devices are powerd via mini-USB, but I don't know if any of the ones openwrt supports, actually have a built in modem.
Check the ToH.
As @frollic suggested, from gl.inet, GL-MT300N-V2. Usb powered and usb connector for any usb 3g/LTE modem compatible openwrt. Tested myself with huawei E3372s
For what it is, very good results with external 4g antennas connected to the E3372s.