Ubuntu – iptables kernel module missing after upgrade from Ubuntu 18.04 -> 20.04

After a release upgrade from Ubuntu 18.04 to 20.04 (focal), the iptables kernel module is missing:

root@server:~# iptables -L
modprobe: FATAL: Module ip_tables not found in directory /lib/modules/5.4.0-42-generic
iptables v1.8.4 (legacy): can't initialize iptables table `filter': Table does not exist (do you need to insmod?)
Perhaps iptables or your kernel needs to be upgraded.

I tried the following, but it did not fix the problem:

sudo apt-get install --reinstall iptables

sudo apt-get install --reinstall linux-headers-$(uname -r)

sudo dpkg-reconfigure iptables
dkms autoinstall

linux-modules-extra is also installed

output of ls -R /var/lib/dkms is:

/var/lib/dkms:
dkms_dbversion  wireguard

/var/lib/dkms/wireguard:
1.0.20200611  kernel-5.4.0-42-generic-x86_64

/var/lib/dkms/wireguard/1.0.20200611:
5.4.0-42-generic  source

/var/lib/dkms/wireguard/1.0.20200611/5.4.0-42-generic:
x86_64

/var/lib/dkms/wireguard/1.0.20200611/5.4.0-42-generic/x86_64:
log  module

/var/lib/dkms/wireguard/1.0.20200611/5.4.0-42-generic/x86_64/log:
make.log

/var/lib/dkms/wireguard/1.0.20200611/5.4.0-42-generic/x86_64/module:
wireguard.ko

Any ideas how I can reactivate iptables?