My installation of Lubuntu 18.04.2 LTS has upgraded to kernel 18.104.22.168 from 4.18.0-25 via Software Update and my Airspy HF+ SDR is no longer recognised. I can get GQRX to recognise it by reverting to the older kernel version. I have seen a comment in ask ubuntu that suggests 18.04 should not be using version 22.214.171.124. Is this upgrade correct?
If you want non-HWE kernels you should install either Lubuntu 18.04 or Lubuntu 18.04.1. All ISO's from .2 onwards have HWE enabled by default (I, along with others are in the process of QA-testing the .3 ISO currently, it should be released Thursday 8 August 2019 though will use the HWE kernel too).
sudo apt full-upgrade either 18.04/18.04.1 or 18.04.2 after installation and they end up the same, except for kernel being used; 18.04.2 using HWE kernel (which will upgrade itself until it finally uses the 20.04 kernel).
Your behavior is consistent with a 18.04.2 installation
See https://wiki.ubuntu.com/Kernel/LTSEnablementStack for details about the HWE or hardware enablement stack kernels. HWE kernels whilst in theory are slightly less stable (less production testing), they have advantages for newer hardware...