"Read more" options - long text on mobile?

Might be beyond scope of support, but thought i'd ask here if there may be an existing or recommended solution.

I've got certain blocks of text that while fine on desktop, are excessively long on mobile. While this is fine for, say, copy it's not working for, say, testiomonials, and I'd ideally like to have a class I could apply to certain sections to make it truncate and show a "read more" link to expnd that section.

Ideally like to avoid JS, and if required keep it tiny.

Any tips?