> At the bottom of this email there is a diff that updates the net/i2pd 
> port to version 2.53.1 and adds a new flavor. This version includes the 
> improvements and fixes from version 2.53.0, as well as some additional 
> important updates [1]. The new flavor adds UPnP support to the net/i2pd 
> port, which is very useful for computers without a fixed IP address 
> within a NAT, as it facilitates incoming I2P connections without the 
> need to configure rules in the router or in pf.conf(5).

I forgot to explain why it is necessary to add a flavor to enable UPnP 
support in this software. The reason is that UPnP support is disabled by 
default on Unix-like operating systems [1]. This means that even if UPnP 
is enabled in the configuration file and the necessary dependency is 
installed, the program will not function correctly unless the CMake 
option WITH_UPNP is set to ON during the build process, or a port is 
statically assigned for incoming connections. However, in some cases, 
assigning a static port is either inconvenient or simply not possible. 
On Windows and Android this option is enabled by default, so it is not 
an unstable or immature feature.

References:
1. https://i2pd.readthedocs.io/en/latest/devs/building/unix/#cmake-options