NTP

Install

sudo apt install ntp

Test

sntp 127.0.0.1
sntp 4.2.8p10@1.3728-o (1)
kod_init_kod_db(): Cannot open KoD db file /var/db/ntp-kod: No such file or directory
2020-03-24 21:45:27.388183 (+0000) -0.001741 +/- 0.332805 127.0.0.1 s3 no-leap

s3 no-leap usually means you are good

vim /etc/nftables.conf

table inet filter {
    chain input {
        udp dport 123 accept
        udp sport 123 accept

systemctl restart nftables

https://www.digitalocean.com/community/tutorials/how-to-configure-ntp-for-use-in-the-ntp-pool-project-on-ubuntu-16-04