Proton rocket is a Russian expendable launcher with a long history. The first rocket took off in 1965, and modern versions of the same tech still remain in use as of 2021. Today, Proton rocket can carry 22.8 tonnes to LEO and 6.3 tonnes to geostationary transfer orbit, which makes it one of the most successful heavyweight rockets in the history of orbital launches.
The Proton rocket is expected to retire by 2030. As of 2018, Russia decided to replace the heavyweight launcher with the Angara rocket. So, it seems unlikely that Proton will sign any new contracts at this point. In case it does, you can find all the latest Proton rocket news here.