Android devices are notoriously well known for the slow rollout of updates. However, for the last few years, lots of OEM has improved the game. Still, many people buy Google’s Pixel devices because they are first to receive any updates. But with Pixel 3a and 3a XL things have changed. Not only they were launched with an older build of Android, but Google has also said that the phones won’t receive security patches till June 3.
If this was not enough, currently you can not sign up for Android Q beta on Pixel 3a and 3a XL. However, if you want, then you can manually download the builds and flash it manually.