Created a custom.css and entered a style with the font-weight changed from 400 (theme/template-20.css) to 700
(I want to change the weight of the h1 tag for page titles)

After clearing the cache the page showed that the custom.css was seen but it was bypassed for the original theme/template-20.css style
Seems like the custom.css is not being observed as the final authority for the theme css
What am I doing wrong or what is my incorrect expectation?

Hello,

If your website is public, can you please provide a direct URL so I can have a look? If it is private, please submit a support ticket.

I have the same issue with RSedimo J4 version.

You can see the page here: csvi.woest-sport.nl

I also feel like the Javascript or so is not properly initiated.

Cheers

I'm not seeing the above CSS rule in your custom.css file, are you sure you or your server isn't using caching? that would explain why this new rule is not present.

I am not the OP. But the problem exists with every rule in the custom.css file.
For example this page
The buttons are grey, should be blue. But custom.css doesn't override the style.css. (nor vm-ltr-site.css and vm-ltr-common.css)

You can compare it to the Joomla 3 version

Hello,

It appears that the component's CSS file is loaded after the custom.css file, thus you will need to defined more specific selectors in order for these to be applied. Note that this isn't template related, you can test the Joomla!'s default user.css file and you'll notice the same behavior.