You can post comment on .edu sites and it will index eventually for free.
Thank you
Those S3-style links come from creating public Twitter Moments and then accessing the hosted version. They're easy to make but hard to index because they’re low authority and often orphan pages. To get them indexed, try embedding the link in a higher-authority page, pinging it, or submitting it in Search Console with a related site. Still, don’t expect huge SEO juice it’s more for diversity than power.