Helix Ultimate 2.0.12 404 custom page not working

I realized it, how do I configure the 404 custom page with the new update?
i don't want to install SPPB only for 404 page

if I opened a ticket it's because I didn't find anything, not even in your documents, forums, guides
I've been looking for a solution for three days
maybe I don't know where to look

I'd made a lot of custom tweaks. Upon updating to 2.0.12 have big layout issues.

Spending hours now to fix when was planning to focus on other things.

Looked OK from front at first because I've got caches, JCH optimise and others.

By the time I flushed and saw the probs it was too late to roll back to back up for other reasons.

If moving up to 2.0.12 definitely backup first, dump caches and check.

Thanks for the advice
My website is still under construction and no optimization software is installed. The cache is clean but all the tests I've done to have a 404 page result in a redirect to home/index.php
For Google, not having a 404 page is an error and I'd like to solve it before putting it online
There is little to look online if this problem is generated by a new version

Hello Eliana,

My 404 is still working with Helix Ultimate 2.0.12, however, I created a custom 404 page based on the instructions here: https://www.joomshaper.com/blog/create-a-custom-joomla-404-page-with-sp-page-builder

Note the instructions re: Edit the error.php file.

That should get you over the line.

I don't want to install SPBB, it just seems too much for the 404 page
I tried without a custom page and it redirect to home/index.php
I tried with:
if (($this->error->getCode()) == '404') {
header('Location: ' . Jroute::_("index.php?option=com_content&view=article&id=2Itemid=261", false));
exit;
}
and it redirect to home/index.php