I don't know unfortunately when it stopped working, because I was using it as a fire and forget solution. Not so long ago I checked it with gufw and was stunned to realize my machine is naked.
root@asus:/etc/ufw# dpkg -l | grep ufw
ii gufw 19.10.0-2
ii ufw 0.36-1
root@asus:/etc/ufw# dpkg -l | grep tables
ii iptables 1.8.4-11
ii iptables-dev:amd64 1.8.3-2
ii libnftables1:amd64 0.9.3-2
ii libnftnl11:amd64 1.1.5-1
ii libxtables-dev:amd64 1.8.4-1
ii libxtables12:amd64 1.8.4-1
ii nftables 0.9.3-2
I'm running with a 5.3.0-3-amd64 kernel.
The actual error:
root@asus:/# ufw enable
ERROR: problem running ufw-init
Bad argument `DROP'
Error occurred at line: 4
Try `iptables-restore -h' or 'iptables-restore --help' for more information.
Bad argument `-'
Error occurred at line: 4
Try `iptables-restore -h' or 'iptables-restore --help' for more information.
iptables-restore: line 2 failed
Bad argument `-'
Error occurred at line: 3
Try `iptables-restore -h' or 'iptables-restore --help' for more information.
Bad argument `-'
Error occurred at line: 3
Try `iptables-restore -h' or 'iptables-restore --help' for more information.
Bad argument `-'
Error occurred at line: 3
Try `iptables-restore -h' or 'iptables-restore --help' for more information.
Bad argument `-'
Error occurred at line: 3
Try `iptables-restore -h' or 'iptables-restore --help' for more information.
iptables-restore v1.8.4 (nf_tables): Chain 'ufw-user-input' does not exist
Error occurred at line: 2
Try `iptables-restore -h' or 'iptables-restore --help' for more information.
Bad argument `DROP'
Error occurred at line: 4
Try `ip6tables-restore -h' or 'ip6tables-restore --help' for more information.
Bad argument `-'
Error occurred at line: 4
Try `ip6tables-restore -h' or 'ip6tables-restore --help' for more information.
ip6tables-restore: line 2 failed
Bad argument `-'
Error occurred at line: 3
Try `ip6tables-restore -h' or 'ip6tables-restore --help' for more information.
Bad argument `-'
Error occurred at line: 3
Try `ip6tables-restore -h' or 'ip6tables-restore --help' for more information.
Bad argument `-'
Error occurred at line: 3
Try `ip6tables-restore -h' or 'ip6tables-restore --help' for more information.
Bad argument `-'
Error occurred at line: 3
Try `ip6tables-restore -h' or 'ip6tables-restore --help' for more information.
ip6tables-restore v1.8.4 (nf_tables): Chain 'ufw6-user-input' does not exist
Error occurred at line: 2
Try `ip6tables-restore -h' or 'ip6tables-restore --help' for more information.
Problem running '/etc/ufw/user.rules'
Problem running '/etc/ufw/user6.rules'
I haven't found any telling hits on this (a lot of ufw problems but not this type). I wonder if it's something with the kernel's iptables support, the fact that nftables package somehow got itself into the installed packages or something else? If I delete the before*.rules or after*.rules from /etc/ufw I get an error because of that, the scripts look for those files.
I wonder if anyone has the same error message for ufw enable. Right now my ufw is inactive.
root@asus:/etc/ufw# lsmod | grep tables
ip6_tables 36864 0
ip_tables 32768 0
x_tables 49152 17 xt_conntrack,nft_compat,xt_LOG,xt_multiport,xt_tcpudp,xt_hashlimit,xt_addrtype,xt_recent,ip6t_rt,xt_comment,ip6_tables,ipt_REJECT,ip_tables,xt_limit,xt_hl,xt_MASQUERADE,ip6t_REJECT
nf_tables 163840 46 nft_compat,nft_counter,nft_chain_nat,nft_limit
nfnetlink 16384 4 nft_compat,nf_conntrack_netlink,nf_tables
