$ sudo apt update
Hit:1 http://deb.debian.org/debian buster-backports InRelease
Hit:2 http://security.debian.org buster/updates InRelease
Hit:3 http://mirror.eu.oneandone.net/debian buster-updates InRelease           
Get:4 http://ftp.de.debian.org/debian buster InRelease [122 kB]                
Get:5 http://ftp.de.debian.org/debian buster/main i386 Packages [7,863 kB]     
Err:6 http://ftp.ntua.gr/pub/linux/mxlinux/antix/buster buster InRelease       
Could not connect to ftp.ntua.gr:80 (147.102.222.211). - connect (111: Connection refused) Could not connect to ftp.ntua.gr:80 (2001:648:2000:de::211), connection timed out
Get:7 http://ftp.de.debian.org/debian buster/main Translation-en [5,968 kB]    
Get:8 http://ftp.de.debian.org/debian buster/contrib i386 Packages [46.0 kB]   
Get:9 http://ftp.de.debian.org/debian buster/contrib Translation-en [44.2 kB]  
Get:10 http://ftp.de.debian.org/debian buster/non-free i386 Packages [76.2 kB] 
Get:11 http://ftp.de.debian.org/debian buster/non-free Translation-en [88.9 kB]
Fetched 14.2 MB in 58s (244 kB/s)                                              
Reading package lists... Done
Building dependency tree       
Reading state information... Done
1 package can be upgraded. Run 'apt list --upgradable' to see it.
W: Failed to fetch http://ftp.ntua.gr/pub/linux/mxlinux/antix/buster/dists/buster/InRelease  Could not connect to ftp.ntua.gr:80 (147.102.222.211). - connect (111: Connection refused) Could not connect to ftp.ntua.gr:80 (2001:648:2000:de::211), connection timed out
W: Some index files failed to download. They have been ignored, or old ones used instead.