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.