This is quite the major change, as currently the list only includes three others. They are also not the same in every European country. And which option appears on the list is determined by a sealed bidding process.
Back in 2018, Google was fined a massive US$5 billion in the EU for forcing its Search and Chrome browsers to be default on Android devices. Following that, Android users in the EU got to choose their default search engine every time they set up or reset their devices. Though as mentioned, this list only included three other options besides Google, and differs from country to country. With the change, users in all of the EU will be able to see a list of up to 12 alternatives. Competing search engine providers will also no longer have to bid to appear on the list anymore. Though this only applies to general search engines that are available for free via the Google Play Store. In its blog post, Google says that these changes will take effect starting from September. (Source: Google [1], [2] via Engadget)