On Ubuntu 20.04, I use the latest self compiled git master version as
shown below:

$ git log -1
commit 5d8608ea744727b9a74874cfe8aca4656a4a9fea (HEAD -> master,
origin/master, origin/HEAD)
Author: Hongyi Zhao <hongyi.zhao@gmail.com>
Date:   Sat Jun 19 12:02:51 2021 +0800

    new file:   .emacs.d/init.company-wordfreq.el
    new file:   .emacs.d/init.lsp-latex
    new file:   .emacs.d/init.straight.el

I noticed the following strange problem:

First start Emacs like this:

$ /usr/local/bin/emacs -Q

Then run `M-x list-input-methods` and scroll down the screen in input
method panel using the mouse or arrow key will cause Emacs
unresponsive for about 1 minute.

See the attached file for the screenshot that was captured when this
problem occurred.

Regards
-- 
Assoc. Prof. Hongyi Zhao <hongyi.zhao@gmail.com>
Theory and Simulation of Materials
Hebei Vocational University of Technology and Engineering
NO. 552 North Gangtie Road, Xingtai, China