Cannot disable DHCP on Debian 11

I have an IBM BladeCenter E with Debian 11 install on a blade server, and I am trying to set up the network with two interfaces (provided on each blade server): one for local network for NFS and one for occasional internet access with static address. NFS works and sometimes the static address did, too... Until I installed LXDE and all the stuff which comes along with it.

In the beginning, I just installed what comes with the Debian 11 netinst distribution on a USB stick because I couldn't set up the network at the time of installation. Then I somehow was able to statically configure the network via /etc/network/interfaces and installed NFS client side and LXDE and some other stuff like GCC and vim, and numpy.

But after I rebooted it to see if the NFS works (which it did), I couldn't connect to the Internet anymore. It keeps now adding dynamic addresses to all interfaces sans lo, in the range 169.254.x.x, which, as I now have learned, means it fails to connect to a DHCP server (because there is no any). There is no NetworkManager or netplan installed, and systemd-networkd is disabled. I tried adding systems configuration as well (as described here: https://forums.debian.net/viewtopic.php?f=5&t=142839&sid=ca6b09a442b04ebec06fbcb6c64f0f9e) but this did not help.

Can anyone please point me towards the possible solutions to this problem? Thanks in advance!

ip a output:

    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: enp16s0f0: <BROADCAST,MULTICAST,DYNAMIC,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether e4:1f:13:18:9c:50 brd ff:ff:ff:ff:ff:ff
    inet 192.168.2.32/24 brd 192.168.2.255 scope global enp16s0f0
       valid_lft forever preferred_lft forever
    inet 169.254.15.226/16 brd 169.254.255.255 scope global enp16s0f0
       valid_lft forever preferred_lft forever
    inet6 fe80::e61f:13ff:fe18:9c50/64 scope link 
       valid_lft forever preferred_lft forever
3: enp16s0f1: <BROADCAST,MULTICAST,DYNAMIC,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether e4:1f:13:18:9c:52 brd ff:ff:ff:ff:ff:ff
    inet 169.254.23.223/16 brd 169.254.255.255 scope global enp16s0f1
       valid_lft forever preferred_lft forever
    inet6 2001:67c:2198:44:e61f:13ff:fe18:9c52/64 scope global dynamic mngtmpaddr 
       valid_lft 2591997sec preferred_lft 604797sec
    inet6 fe80::e61f:13ff:fe18:9c52/64 scope link 
       valid_lft forever preferred_lft forever
4: enxe61f13199c53: <BROADCAST,MULTICAST,DYNAMIC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN group default qlen 1000
    link/ether e6:1f:13:19:9c:53 brd ff:ff:ff:ff:ff:ff
    inet 169.254.130.234/16 brd 169.254.255.255 scope global enxe61f13199c53
       valid_lft forever preferred_lft forever
    inet6 fe80::e41f:13ff:fe19:9c53/64 scope link 
       valid_lft forever preferred_lft forever

And here are the contents of /etc/network/interfaces :

# and how to activate them. For more information, see interfaces(5).

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

auto enp16s0f0
iface enp16s0f0 inet static
address 192.168.2.32
netmask 255.255.255.0


# The primary network interface
allow-hotplug enp16s0f1
auto enp16s0f1
iface enp16s0f1 inet static
address A-PERFECTLY-VALID-IP-ADDREESS
netmask 255.255.255.0
gateway A-WORKING-GATEWAY-ADDRESS
## dns-* options are implemented by the resolvconf package, if installed
#dns-nameservers WORKING-DNS-SERVER-ADDRESS1 WORKING-DNS-SERVER-ADDRESs2 8.8.8.8

Also:

root@lomc32:/home/igors# systemctl status networking.service
● networking.service - Raise network interfaces
     Loaded: loaded (/lib/systemd/system/networking.service; enabled; vendor preset: enabled)
     Active: active (exited) since Sat 2022-06-04 16:57:47 EEST; 5min ago
       Docs: man:interfaces(5)
    Process: 593 ExecStart=/sbin/ifup -a --read-environment (code=exited, status=0/SUCCESS)
   Main PID: 593 (code=exited, status=0/SUCCESS)
        CPU: 48ms

Jun 04 16:57:47 lomc32 systemd[1]: Starting Raise network interfaces...
Jun 04 16:57:47 lomc32 systemd[1]: Finished Raise network interfaces.


root@lomc32:/home/igors# systemctl status networkd.service
Unit networkd.service could not be found.

I also tried adding the systemd-networkd configuration as described in the link above, with the same information as in /etc/network/interfaces (/etc/systemd/networkd.conf has all lines commented out) but this did not help.

Also, I tried removing some DHCP-related software:

apt remove dhcpcd5 isc-dhcp-client isc-dhcp-common

Of which dhcpcd5 was not installed anyway but this did it help either.