The LGPS rules changed from 1 October 2023 because of the McCloud remedy. The changes are backdated to 1 April 2014, when the career average scheme started. If you qualify for underpin protection, you will be protected even if you have already left the LGPS or taken your pension.
The LGPS Member website provides all the information required to understand the remedy and they have produced a short video for you to watch, and you can see if you are effected with their online tool.