As you may know all (almost) network messaging comes in pairs with outbound packets getting inbound responses. I use tcpdump to look at that to show what happens on an interface, like:

tcpdump -n -i wlan0

to see packets in to and out from wlan0 without attempting "reverse dns" on them (i.e. see IP addresses rather than domain names).

You do that in one terminal while using an other terminal for trying things like ping. The best is if you can do the same on the target host, to see where the messages hold-up may be. Note that for ipv4 it is essential that "arp" messaging move freely; the hosts use that so as to learn the ethernet addresses of LAN devices. All networking is carried by the link-level LAN connectivity, which uses the ethernet addresses or broadcasts (i.e. address ff:ff:ff:ff:ff:ff plus the broadcast flag bit set). 

In your case, I do suspect your router. I think that most routers have "broadcast groups" where they only forward broadcast messages to interfaces within the group of the interface where the messages come in. Which router do you have -- brand and version "number"? (with that we can probably find its instruction book on the Internet)

Routers may also have limitations on number of connected devices.

I have no idea what the synaptics program does.

At a guess you have setup multiarch (perhaps an amd64 machine with arm64 as foreign architecture) and librewolf have published different most recent versions of their package in those architectures. To solve that "normally" you'd add an attribute like "[arch=amd64]" for the repository line, making it be like

deb [arch=amd64] http://repo.librewolf.net librewolf main

Doing so would focus that repository line to apply for the nominated architecture only. (Use a comma separated value list to nominate more architectures)

But that's all guess work.

Yes it sounds like the installation (not liveCD) has something wrong.

Does it have a firewall? e.g. does iptables-save report something; (or if you use nftables there would be a similar command among its programs). And use ip6tables-save for ipv6 rules. (I'm not sure about the nftables commands)

Is the interface up? ifconfig wlan0 would be the easiest, if you have net-tools installed. An you'd also check with ip link show dev wlan0 and ip address show dev wlan0. The ip command comes from the iproute2 package.

Is there a default route? ip route show ... and checking ipv6: ip -6 route show

Hmm but if understand right, the laptop does have other internet access... anyhow, please include the outputs of those commands and we'll see if there's something to see there.

No, service management should not be a brick because it needs openness and flexibility. In my mind, my words were rather an attempt to explain why one might raise the questions you raised; my view is that a service management system needs to be open and flexible in order to be useful in a multitude of circumstances.

Are you seeking answers really, or are you seeking questions? Don't you wish to come to conclusions about those questions you ask, or do you prefer to side step and ask similar or new questions about other sub systems? Why don't you focus on individual functions. such as partitioning or file manager or keyboard mapping?

It could.

yes it adds overhead; every block access needs to go through the mapping tables.

Well "Devuan" is actually like a warehouse of software rather than a particular distribution so it all depends on which particular setup you want to have. The most recent "excalibur netinstall", which provides a range of distribution choices with the most recent software, will want at least 800 Mb RAM to run and would comfortably install most of its graphical desktop environments on an 8 Gb disk. Though, today one will want at least 20 Gb disk to be somewhat "future proof".

Almost all software is compiled for several architectures, including both 32-bit and 64 architectures. In debian parlance they have names like i386, amd64, armel, armhf, arm64, risc64, ppc64el etc.

The keyword is "Choice".

I'd guess your "I chose RUNIT" means to install some software, and your /etc/apt/sources.list nominates /media/cdrom as a repository (of cdrom type), which is one of the babies that came with the installation. If you remove that, or comment it out, in /etc/apt/sources.list your system (aka "it") will no longer ask for that repository.

Since the analog out put is on your card 1, you should create a file
/etc/alsa/conf.d/00-defaults.conf with the following line:

defaults.pcm.!card 1

That doesn't sound like an active mirror but I guess you looked carefully in devuan_excalibur/installer-iso/.
The mirrors are otherwise listed at https://www.devuan.org/get-devuan and if you find an inactive one you could "report" that eg as a "devuan-www" bug at https:///bugs.devuan.org.

Very peculiar opinions you are voicing there. Especially I would consider "GUI tool that makes configuring it for online use" being a quite oxymoronic phrase. It's kind of like saying: "but he is friendly to the kids". Of course, I voice my opinion here.

Bring up a terminal and use the command

pkill Xorg

(as the user that owns the Xorg process)