Why do you want to do that?
You can try throug sideload see if it takes , but then your OS is not up to date and how long your going avoid updating to 12 .How do I go back to Google 11 from Google 12
I'm own a Pixel 5. If I could, I'd go back to 11 in a heartbeat. Not enough improvements to warrant the upgrade for me, numerous bugs, battery life is worse, All sorts of UI controls that are worse in my opinion. It's one of the worse update ever from Google. And I'm not the only one that feels that way. I feel it was rushed due to the release of the Pixel 6 and 6 Pro. They should have left it in Beta and released the new phones with 11. But then again, that's JMHO.
I think there's always a period of adjustment with any major update. I'm having no issues with Android 12 on my Pixel 3a XL. The UX design changes don't really bother me.
You would have to unlock the bootloader, and then it will allow you to flash a factory image of an earlier software versionHow do I go back to Google 11 from Google 12
The very dim lock screen, AT A GLANCE omissions, and especially the non-functional battery % on the status bar are my issues.