The Use of Multiple H1 in the content wont effect the SEO, but semantic headers are still used by Google to comprehend the context of different portions of your pages.
“Our systems don’t have a problem when it comes to multiple H1 headings on a page,”.John Mueller, Google
“We use headings to better understand the context of different parts of a page,”
Multiple H1 headings don’t bother Google’s AI, as the fact is it’s “a rather frequent practice on the web,” and the distinction is negligible for visitors (either the Multiple H1 is used or not); and both types of pages can be very relevant to a topic or question they have.”
While Creating the Website SEO shouldn’t be the primary objective, your primary objective should be to create Quality content for target audience that help them to solve there problem or take decision, making your information accessible to them, whether through the use of multiple H1 headers or other conventional HTML elements, will not obstruct your SEO efforts.
If you’ve inherited a site with numerous H1s, it might not be worth your time to reformat them all. However, because Google uses headings to comprehend the context of different portions of your pages, adding headings to essential sections that don’t have them may be helpful.