As the stable build is capable of OTA version upgrade from Android 11 (R) to Android 12 (S) according to OS OTA upgrades I would assume that any required vendor blobs must be present in the stable OTA upgrade, and thus in the ROM itself.
If I had the device with /e/OS R dev installed, I would firstly consider downloading the dev and stable Android 12 (S) ROMs and see with a payload dumper how different the ROMs were. Specifically looking for evidence of vendor partitions or upgrade firmware.
I guess I would also consider the risks of changing dev to stable at my current Android R (after I had done a full backup and reduced my installed apps to essential).
I answered a different question with similar issues here: [Walkthrough] Extract eRecovery and boot images using payload-dumper-go - #3 by mihi. Perhaps the reply was both over cautious while not too discouraging (??) – as it happened there was a happy outcome reported in the end.
The requirement for experimentation is courage and a transferable backup of essentials.