Yeah. It looks like it is a permissions issue. Usually in linux you have to use chmod for modifying. Doing ls -l should say the permissions. For example when you create a folder, you should get the following permissions by default: drwxr-xr-x So doing chmod 644 will give it drw-r--r-- permissions. If you really don't care that anyone could read and write, you could do chmod 777 on the folder
do you notice that it stops the internal server for the singleplayer worlds. here are some lines that you should take a look: [11Oct2025 00:02:01.774] [Render thread/INFO][rgp_client/]: Reconnected Rocket client as session has become inactive.
[11Oct2025 00:02:01.810] [Server thread/INFO][net.minecraft.server.network.ServerGamePacketListenerImpl/]: ItsOutCast lost connection: Disconnected
[11Oct2025 00:02:01.810] [Server thread/INFO][net.minecraft.server.MinecraftServer/]: ItsOutCast left the game
[11Oct2025 00:02:01.845] [Server thread/INFO][net.minecraft.server.network.ServerCommonPacketListenerImpl/]: Stopping singleplayer server as player logged out
[11Oct2025 00:02:02.085] [Server thread/INFO][net.creeperhost.ftbbackups.FTBBackups/]: Shutdown Complete
[11Oct2025 00:02:02.091] [Render thread/INFO][mezz.jei.library.startup.JeiStarter/]: Stopping JEI
[11Oct2025 00:02:02.092] [Render thread/INFO][mezz.jei.library.load.PluginCaller/]: Sending Runtime Unavailable...
[11Oct2025 00:02:02.092] [Render thread/INFO][mezz.jei.neoforge.plugins.neoforge.NeoForgeGuiPlugin/]: Stopping JEI GUI
Did you have the world folder in the saves folder? Since it is the folder where worlds are located.
To play with the official minecraft launcher you need forge installed. After that you can make a folder called mods in .Minecraft folder and you can now put mods to it!