It would be really nice if there is a GUI way to changed the installed kernel in Solus.

There are only 2 kernels and most people use the default one. Developing a GUI for a one time use for a small portion of the users would be counter productive there are tons of more important things.

Currently on Solus has 2 options for kernels:

  1. LTS (currently 4.9) - Long Term Support, which few people need to use if they have compatibility problems or need to use proprietary Nvidia driver for old cards (340).
  2. Current (currently 5.5.7) - the default, as new kernel as possible that doesn't cause problems.

If something is broken with a kernel, you should report it so it can be fixed for everybody.
Also when updating, system will keep the previous one, if something goes wrong. And you can boot to it if you press space repeatedly during boot.