I wasn't able to recreate this behavior in 26.1 Snapshot 1. I could still deal melee damage to the ender dragon while it was perched on top of the bedrock. Could you please provide more details regarding the problem you're facing? Videos and/or screenshots would be greatly appreciated.
Do you have Touchscreen mode enabled? I wasn’t able to recreate the behavior you described.
Please see if community support can help resolve your issue. Please link to this bug report when asking for help with your issue.
This is a translation issue and not an actual bug with the game. Translations are handled via Crowdin.
Also affects copper chests and its variants.
Here’s a narrated video explaining the problem.
Reopening as this issue is not fixed in 25w46a. Performing both the jabbing and charging attacks at the same time is still possible.
This was originally a bug as stated in MC-181190, which has been fixed. The behavior you are experiencing is intended.