I doubt that this will run into any 1A issues. It will probably pass the test for allowable time/place/manner restrictions.

• It is content neutral.

• The government can probably show a significant government interest in reducing the harms infinite scroll often leads to.

• It is narrowly tailored. It achieves the goal without burdening more speech than is substantially necessary to achieve the goal. Arguably it doesn't burden any speech since every word you can have on an infinite scroll page you can have on a paginated site.

• There are alternate channels. The speakers still can get their message across. In this case they can get it across to the exact same audience in the exact same place. They just have to stick in page breaks.