No LTE on samsung s4 mini?
As you already know, LineageOS explicitly offers different ROMs for the 3 variants: serrano3gxx (GT-I9190, 3G single-SIM), serranodsdd (GT-I9192, 3G dual-SIM) and serranoltexx (GT-I9195, LTE single-SIM).

The assert checks embedded within the packages will prevent them from being flashed on the wrong variant of device, but this is given that you installed the correct recovery for your variant as well (for which there are no similar assert checks).

With the correct ROM and recovery, if you're still not getting LTE, you should try forcing LTE in Settings. Also be aware that the device itself is a rather early LTE device and as such has very limited LTE band support; PhoneDB shows support for only LTE B3/B7/B20. If your carrier doesn't use any of these bands then naturally you won't get LTE whatsoever.