Qualify outbound links to tell Google your relationship with the linked page.

Source: https://developers.google.com/search/docs/crawling-indexing/qualify-outbound-links

• rel=”sponsored”
  for ads, paid, sponsored links etc
• rel=”ugc”
  for user-generated content, e.g. response to forum posts
• rel=”nofollow”
  if you do not want to pass on a link value
• Combination: <a href=”https://www.link.nl” rel=”sponsored, nofollow”>Linktekst</a>