Joomla 4 Introduces a Modular Approach for Interactive Components
https://docs.joomla.org/J4.x:Using_Bootstrap_Components_in_Joomla_4

Joomla 4 Introduces a Modular Approach for Interactive Components https://docs.joomla.org/J4.x:Using_Bootstrap_Components_in_Joomla_4

Ok. I added the code
\Joomla\CMS\HTML\HTMLHelper::_('bootstrap.collapse', '.selector', []);
To FlexiContent template and now it works.

But how to add this code in Gantry5 template?
Maybe we need PHP atom or particle?

If you are using Gantry you can add bootstrap in a basic outline for the entire site or a dedicated outline, page settings tab -> Head Properties -> Custom Content

Is it ok?

You probably need to return the link from the cdn.
https://getbootstrap.com/docs/4.0/getting-started/introduction/
or from your joomla you will find in
media/vendor/bootstrap

for example

You can use this plugin and create a suitable module and publish it to gantry using the module instance particle
https://github.com/ceford/j4xdemos-mod-custom-bscompos/raw/master/mod_custom_bscompos.zip