Earlier this month, Google launched the Pixel 4a (code-name "sunfish"), the company's second mid-range Pixel smartphone. At a price of $349, you get a 5.81" OLED display, the Qualcomm Snapdragon 730G, 6GB of LPDDR4X RAM, 128GB of UFS 2.1 storage, a 3140 mAh battery, a 3.5mm audio jack, and Google's excellent camera and software support. Late last week, the phone officially went on sale, and today, Google has uploaded all the tools, files, and documentation needed by developers interested in running custom software.
When Google released Android 11 Beta 3, they promised to eventually make the beta available for the Pixel 4a. If you have the device, you can now opt into the Android Beta Program, allowing you to receive an OTA update to the latest Android beta release. If you don't want to wait for the beta to roll out, you can alternatively flash the Android 11 Beta 3 factory image or sideload the full OTA file. The build number is rpb3.200720.005, which matches the builds for the other Pixel phones currently eligible for the Android 11 beta.
Download Android 11 Beta 3 for the Google Pixel 4a: Opt into Android Beta Program ||| Factory Image ||| OTA
If you want to return to the stock software on the Pixel 4a, you can extract and flash the latest factory image firmware from the link below. The latest build carries a build number of QD4A.200805.003, corresponding to the August 2020 Android Security Patch Level. There are two sets of factory images available: One for JP/Verizon units and another for unlocked units.
Lastly, Google has uploaded the device tree and kernel source code for the device. These will be helpful starting points for any developer interested in building a custom kernel to boot TWRP and/or an AOSP-based custom ROM.
Factory Images ||| Device Tree
Kernel Source Code: Android 10.0.0 Release 0.87 ||| Android 10 Beta 3 Release 0.6 ||| Prebuilt binaries