If you just want to get started experimenting without building any physical networks, you are welcome to join the Public Reticulum Testnet. The testnet is just that, an informal network for testing and experimenting. It will be up most of the time, and anyone can join, but it also means that there's no guarantees for service availability.
The testnet runs the very latest version of Reticulum (often even a short while before it is publicly released). Sometimes experimental versions of Reticulum might be deployed to nodes on the testnet, which means strange behaviour can occur. If none of that scares you, you can join the testnet via either TCP or I2P.
Just add one of the following interfaces to your Reticulum configuration file:
# TCP/IP interface to the Dublin Hub
[[RNS Testnet Dublin]]
type = TCPClientInterface
enabled = yes
target_host = dublin.connect.reticulum.network
target_port = 4965
# TCP/IP interface to the BetweenTheBorders Hub (community-provided)
[[RNS Testnet BetweenTheBorders]]
type = TCPClientInterface
enabled = yes
target_host = betweentheborders.com
target_port = 4242
# Interface to I2P Hub A
[[RNS Testnet I2P Hub A]]
type = I2PInterface
enabled = yes
peers = mrwqlsioq4hoo2lmeeud7dkfscnm7yxak7dmiyvsrnpfag3z5tsq.b32.i2p
The testnet also contains a number of Nomad Network nodes, and LXMF propagation nodes.