I used freedns.afraid.org more than 5 years. It requires to confirm
an account only once a year. But it is inconvenient anyway. After a
year nobody remember to authorize and confirm. Just panic and no
connection. So in case of remote access, I'm preferring to connect
the sites to my central office through OpenVPN or Wireguard. Only
office should have static IP. The clients - the sites are connected
to the office by VPN cnannels. So I can control any object though
my own VPN connection to the office. Office router firewall is controlling the traffic and isolates the sites to limit the harm of an intrusion at single site.