Java Edition rarity was fixed in 25w34a to Rare (MC-276931 ).
On Bedrock 1.21.110.25 Preview the rarity is still Common.
I also had this issue on PS5 on 1.21.90. Our world was created before the Nether Update, and we have killed the dragon 20+ times already before respawning and killing it again.
Update: Still an issue in 1.21.100. See for more info: REALMS-13267
Fixed just now.
Fixed just now.
Update: Custom Commands are now available without in-game cheats in 1.21.90
with @minecraft/[email protected]
Related Bedrock bug report: MCPE-227032