Question Which Ads package to use?

Hi @tvvladimir
Allow me to clear things up a bit;
Advertisement (legacy) is Unity's ad network. We used to encourage users to use this ad solution directly, but phased out this approach to encourage users to use a Mediation solution instead, as it will yield more revenues, and people who make more money are happy, and we like happy users. Unity's ad network is not going anywhere, we are just encouraging users to use it through a Mediation solution instead.

Advertisement with Mediation (com.unity.services.mediation) is Unity's Mediation solution. Since Unity merged with ironSource last year, we have stopped development on that Mediation solution, and focused our efforts on ironSource's Mediation solution. While we still support this solution, we encourage users currently using it to migrate to ironSource's solution, as Unity Mediation will be retired eventually. Note that the dashboard does not allow new projects to use this Mediation solution.

Ads Mediation (com.unity.services.levelplay) is ironSource's LevelPlay Mediation. This is the solution where we are currently focusing our efforts. LevelPlay is widely used in the industry, and our intent is to integrate it with Unity's editor to make it as convenient as possible to use. We recommend using this solution.

As for updating Unity, if you are starting a new project I would recommend updating to the most recent version, but our package supports all LTS versions, and may work on older versions, with no guarantees.