If you only need nextcloud on your local network, a quick and dirty way of assigning hostnames to machines is the hosts file. Obviously, this has to be done on every computer from which you wish to access nextcloud. Also, nonrooted mobile OSs don’t let you edit the hosts file.

Alternatively, you can set up a local DNS server. Pihole also has that capability (I personally had mixed results with Pihole, not sure if I did something wrong). Some routers may have that too.

If you need it public on the internet, yes, you need a domain name. Some providers offer free domains (but it will be a subdomain of the provider). Something to keep in mind is that your IP is probably dynamic. When you connect to the Internet, the ISP assigns you a random IP address from their pool of IPs. To keep the domain up to date, you will need to setup a dynamic DNS solution. This is a simple script/program that periodically checks your IP, and if it changes, updates that domain automatically.

Plenty of free hostname providers. I use Dynu

You don’t need to especially not in your local network, but if you want to expose it to the internet then it would definitely make sense since you need a domain in order to use SSL encryption.

It can be an ip address, if you have a static ip. If you’re planning to host this on the open internet and have a dynamic ip (home internet is most likely for this), or static and don’t want to pay for a top level domain you can use a service like noip.com for a free address like “test.ddns.net”

You can also change this after the initial setup in Nextcloud’s config.php as well as as additional domain names/ip addresses that can reach the server.

I’m not very familiar with NextCloud but you can use something like duckDns to direct traffic to your ip for free. Still an actual domain is a bit nicer if you want to share the URL.

Just buy a real domain name from Cloudflare. They’re incredibly cheap dude. And you can use cloudflare’s dns stuff for free

You can purchase one, or as a first step you can use duckdns.org which is entirely free! Then when you think you want your own domain name you could just switch :-)

DuckDNS

Depending on what you are trying to do, not necessarily. NextCloud itself doesn’t really care, as far as I know, as long as it’s address doesn’t change. AIO on the other hand is setup in such a way that it needs a resolvable domain name and a valid certificate for https.

This could be done by spinning up your own certificate authority and dns server, but that is a lot of extra work and would be local network access only.

Another way would be to use a free domain and a free certificate from let’s encrypt. The downside here is that the domain authority could yank your domain at any time, for any reason (as happened to all of the free .ml domains recently). At which point your certificate would also stop working resulting in a situation where you may have to nuke and pave.

If you want to be local access only, I would pick an install path other than AIO. If you want to be able to access NextCloud remotely, purchase a domain name.

A VPN, such as TailScale would be considered local network in this situation.

Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I’ve seen in this thread:

7 acronyms in this thread; the most compressed thread commented on today has 5 acronyms.

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I’m not sure how nextcloud handles it, but as long as you can resolve the domain then you can put whatever you want.
You usually purchase a domain so it appears in the internet with the major DNS’, but if you only have the site in your internal network then you can put whatever you want as long as you update your internal DNS.

Usually you can do this by manually updating the hosts file in your machines.
But a better way is to have something like PiHole, in which you can set your local DNS to resolve to your own IP.
After that the only annoyance are the SSL certificates which will be selfsigned since browsers show a warning but some services don’t have a way to work with them.

I run my Nextcloud behind Tailscale, and Caddy handles theTailscale https certs.

You can also use Tailscale Tunnel which will give you an subdomain to access for free.

Or full hardcore and use Tor .onion domain. Completely free with additional privacy.