What command can be used on an existing (formatted) partition, to configure the interval between disk checks when mounting partitions?

e2fsckconfig is not a valid or standard Linux filesystem utility command.

tune2fs adjusts filesystem parameters stored in the superblock of an existing ext2/ext3/ext4 partition without reformatting it. The -i option sets the maximum time interval between forced filesystem checks and -c sets the maximum number of mounts before a check is triggered. These settings are applied directly to the already-formatted filesystem in place.

mke2fs creates (formats) a new ext filesystem from scratch and cannot be used to reconfigure an already-existing partition.

config2fs is not a real Linux command and does not exist in standard distributions.

e2fsck is the ext filesystem checker and repair tool used to scan and fix filesystem errors, not to configure check intervals.