It’s not hard to find private RuneScape server or RSPS. The fact is that since 2007 it has became rather easy to find private runescape servers due to the launch of RuneLocus’ RSPS List and soon after that many others followed in the years to come.
You can find a safe RuneScape private server by checking one of the RSPS lists: https://serverlist101.com/runescape-servers/
Which private RuneScape servers are the best? That depends on your wants and needs, but mainly you want to pick RSPS server that was around for awhile and won’t shut down tomorrow as that would result in lost progress and we all hate that.
Just be sure to check out individual server website and their staff team, that should give you some ideas on how specific private RuneScape server is operated and if it is the server with good track record.