Ungoogled-chromium goes down after system update

Custom packages will almost always require a rebuild after a major update - especially on stable branch.

You should be aware that you need to be on Manjaro unstable branch to be able to use AUR.

Execute the following command - it should provide a similar response - that is - if you want to run custom packages using AUR

 $ sudo pacman-mirrors -G
unstable

ungoogled-chromium-bin run fine on unstable branch

Do not replace system libraries with custom packages from AUR - not ever…

Refreshing your mirror list will not provide any changes that affects building custom packages from AUR.

Assuming there is no packaging issues - the following is the recommended approach

sudo pacman-mirrors -aS unstable
sudo pacman -Syu base-devel --needed
git clone https://aur.archlinux.org/ungoogled-chromium
cd ungoogled-chromium
makepkg -iscC

And yes - relying on a package like ungoogled-chromium is a pain - the only way you can remain stable in such case is to create a local (portable) mirror