Re: Run `M-x list-input-methods` and then scroll down the screen in input method panel using the mouse or arrow key will cause Emacs unresponsive for about 1 minite.

[Eli Zaretskii]

> From: Hongyi Zhao <hongyi.zhao@gmail.com>
> Date: Sat, 19 Jun 2021 17:47:18 +0800
> Cc: emacs-devel@gnu.org
> 
> Either way, as shown below:
> 
> $ /usr/bin/emacs
> $ /usr/bin/emacs -Q
> 
> And both the following two commands completed instantly:
> 
> M-x list-input-methods RET
> C-h h

They also do that in my build, so the question is what is different
between your "slow" build and the "fast" build.  You need to find out
and tell us what are the differences between them in terms of
configuration, supported features, optional libraries, etc.