What config to change

1.18 snapshots re-introduced telemetry.
https://www.minecraft.net/en-us/article/minecraft-snapshot-21w38a

Why should it be changed

Telemetry is not necessarily a bad thing (if done privately), but sending telemetry to Mojang from a modded instance doesn't really help anyone.

Category

Vanilla option

Additional details

https://github.com/kb-1000/no-telemetry
https://modrinth.com/mod/no-telemetry
https://curseforge.com/minecraft/mc-mods/no-telemetry/

but there probably will be a vanilla option later

Edit: https://bugs.mojang.com/browse/MC-237493 (closed as "works as intended") and discussion on https://www.reddit.com/r/Minecraft/comments/pzatop/telemetry_snooper_useridentifiable_data/

Just an update for new users that get confused:
Telemetry has been disabled from the day 1.18 was introduced and it will be done so in the future, just the mod that provides it has been swapped and may be swapped in the future.

You'll find the mod that currently disables it on the changed options wiki.