If you use the /ride command to summon an Enderdragon in a Minecart or a Boat you can't kill him with strength 255. He will turn red if you try it.
Linked issues
Comments 1
MCPE-105902
Can't kill Enderdragon in Minecarts/Boats
Resolved
Duplicate
1
Fichi
(Unassigned)
Unconfirmed
Nintendo Switch
Nintendo Switch
1.16.100
Retrieved
The issue isn't the boat, it's that strength 255 is not functional. See MCPE-20469.
You might want to try strength 20.