Howto Disable HTTP2 in Nginx

For version < 1.25 (Ubuntu 20.04 LTS and 22.04 LTS have 1.18, Ubuntu 24.04 has 1.24):

• remove http2 statement from listen line in virtual hosts

For version >= 1.25 - if you are using an official repository (but some plugins from Ubuntu are only in paid Plus version) or other distro:

• add or set http2 off; line in virtual hosts

In both cases HTTP2 cannot be disabled selectively only for specific hosts (I tried different subdomains), you need to disable IPv4 listens in all virtual hosts and then it will be disabled for IPv4 protocol. The same applies to IPv6 listens.