Looks like Android 12 will let you use two SIMs on Pixel 4a 5G and Pixel 5 without any trade off - Android

It appears that  will let you use two SIMs on Google's ready smartphones without any limitation. 

Unlike the Google Pixel 3a and later phones, the  and  don't let you take full advantage of the Dual SIM Dual Standby (DSDS) option. This could change with Android 12, reports , citing a .

DSDS lets you use two SIM cards simultaneously - a physical SIM card and an eSIM. Users can decide which SIM to use for which action, which means you can use one carrier for calls and texts, and another for data.

On the Pixel 4a 5G ...