I concur with what @nodsocket said, but I will go a step further and suggest to not buy that device (as it seems you're looking to buy, and don't own that device already).
Pixel 4a will be end of life very soon, and won't be secure anymore.
I would recommend a 6th/7th gen Pixel device, which while likely more expensive, will last very long with official support.
Recommended devices: https://grapheneos.org/faq#recommended-devices
Device lifetime: https://grapheneos.org/faq#device-lifetime