How to kernel downgrade?

So I need to downgrade the kernel of my rpi 4 due to a kodi (or general) issue with h265 since recent versions.
https://github.com/raspberrypi/linux/issues/4112
The proposed workaround is to downgrade using:
sudo BRANCH=stable rpi-update b7c8ef64ea24435519f05c38a2238658908c038e
We don’t have rpi-update, how could i run this?

Thanks!

Hello,
Running apt install rpi-update should install it so you can run the command.

it was so obvious, thanks!

I have also the same question, thanks