added install instructions for fedora and ubuntu

May not work, I have not tested it.

README.md

@@ -45,11 +45,10 @@ with anyone currently at risk of death in overcrowded prisons.
 - Linux kernel with batman-adv module
 - [iwd][]
 - python
-- python-setuptools (for building)
+- python-setuptools (for building and installing)
 - [dasbus][]
 - WiFi adapter with ad-hoc support
 - two or more computers, or laptops with WiFi adapter, called nodes
-- systemd-resolved (optional, for DNS)
 - batctl (optional, for debugging)
 - python pip (optional, for uninstalling)
 
@@ -71,16 +70,53 @@ Optionally, [setup systemd-resolved][arch-resolved] for DNS if any
 of the nodes have internet access. [Start naxalnet][startnx] when
 you need it.
 
+### Ubuntu
+
+naxalnet is not packaged for Ubuntu, so you will have to build
+and install it manually.
+Currently, only the [unreleased 21.10][ubuntu-systemd] comes with the
+required version of systemd. Therefore, naxalnet won't work on Ubuntu
+21.04 or older.
+
+<!-- TODO: remove this message when systemd 248 arrives in 21.04 -->
+
+Install the requirements from the Ubuntu repositories:
+
+```sh
+# batctl is optional
+pkcon install systemd python3-pip iwd batctl
+# Now, install dasbus with pip
+pkexec pip3 install dasbus
+```
+
+Now follow the instructions in the
+[manual installation section][install-manual]
+
+### Fedora
+
+naxalnet is not packaged for Fedora, so it should be installed
+manually. naxalnet requires atleast systemd v248 which is only
+available on Fedora 34 and above. Install the dependencies:
+
+```sh
+# systemd-resolved may be required for rawhide
+pkcon install systemd-networkd iwd python3-dasbus python3-setuptools
+```
+
+Now head over to the [next section][install-manual] to install naxalnet.
+
 ### Manually
 
-Clone the repo and cd into it.
+Install the [requirements][requirements].
+
+Clone the naxalnet repo and cd into it.
 
 ```sh
 git clone https://git.disroot.org/pranav/naxalnet.git
 cd naxalnet
 ```
 
-Or, if you have an [IPFS client][ipfs] running, try:
+Or, if you have an [IPFS client][ipfs] running, try this instead:
 
 ```sh
 git clone http://k51qzi5uqu5dlye74be0n9iihwk6sm54vexo7bf7pdr4w811y6mmrcp25djozv.ipns.localhost:8080/naxalnet.git
@@ -272,3 +308,6 @@ See [LICENSE](LICENSE) for the complete version of the license.
 [iwd]: https://iwd.wiki.kernel.org "WiFi daemon"
 [free-sw]: https://gnu.org/philosophy/free-sw.html "What is free software?"
 [enablenx]: #running-at-boot
+[ubuntu-systemd]: https://packages.ubuntu.com/impish/systemd
+[requirements]: #requirements
+[install-manual]: #manually