Is there a way to lock head rotation? 1.14.4
Solution 1:
You could use a command that could move the players head down by a certain value each time. This would mean that instead of locking down, it will smoothly go down at a fast rate. The problem with this is that it will be easier for them to just move their head more, as the process will be slower.
Other than that there is no way to prevent people moving their heads without using some plugins or mods. Hope this was helpful somewhat, sorry about that.