Apt update readings lists very slow

If I’m not mistaken, it was introduced in one of the last releases. If needed you could deactivate the compressed feature as follow

echo 'Acquire::GzipIndexes "false";' > /etc/apt/apt.conf.d/98dietpi-uncompressed
/boot/dietpi/func/dietpi-set_software apt-cache clean
apt update

On my RPI3B+, apt update execution time reduced from 20s down to 6s

Before

root@DietPi3:~# time apt update
Hit:1 http://raspbian.raspberrypi.org/raspbian buster InRelease
Hit:2 https://archive.raspberrypi.org/debian buster InRelease
Reading package lists... Done
Building dependency tree
Reading state information... Done
1 package can be upgraded. Run 'apt list --upgradable' to see it.

real    0m19.475s
user    0m19.106s
sys     0m0.449s
root@DietPi3:~#

After

root@DietPi3:/etc/apt/apt.conf.d# time apt update
Hit:1 https://archive.raspberrypi.org/debian buster InRelease
Hit:2 http://raspbian.raspberrypi.org/raspbian buster InRelease
Reading package lists... Done
Building dependency tree
Reading state information... Done
1 package can be upgraded. Run 'apt list --upgradable' to see it.

real    0m6.336s
user    0m5.005s
sys     0m0.496s
root@DietPi3:/etc/apt/apt.conf.d#