I'm not certain but I think I read that switching OS does not solve the issue you allude to since it's firmware related.
Following the #Pixel4a battery downgrade debacle https://wiki.rossmanngroup.com/wiki/Pixel_4a_Battery_Performance_Program I'm considering switching to a custom ROM…
#CalyxOS in particular seems very neat – does anyone have experiences with it? I'm not sure how it compares to #GrapheneOS? Or, seeing how the Pixel 4a is "end of life" for both of them, should I just go with #LineageOS?
Discussion
Oh and ofc Pixel 4a has been EOL for a long time. It' simply not secure any more. Apart from that, GrapheneOS only has advantages compared to Calyx or Lineage. My heartful advice is to get a Pixel 8a and install GrapheneOS. The Pixel 8a still has around 5 years of full support for the full software stack pledged by Google and comes with decisive hardware security benefits (e.g. MTE) that GrapheneOS fully leverages. It's quite cheap and you might be able to trade in your Pixel 4 to get some cash back.