My problem is the following. I open my server from RSM and when I install the oxide mod it immediately sends my server to moded. but I saw a lot of people who have mods on their community servers. my question would be how to make my community server X2

You can't, it's not allowed, and those people who do it will get blacklisted in the end anyway.
https://support.facepunchstudios.com/hc/en-us/articles/360009062817-Guidelines-for-community-servers-using-plugins-mods