OK, I removed those from one system but now that system cannot connect to anything online. It's like the network driver or DNS or something is broken. This latest update has apparently broken something. I'll definitely wait before updating the others....

Proposed repositories? What are those? The only thing remotely experimental in my sources.list is backports. Do they put kernels into backports? Should I roll back somehow?

deb http://deb.devuan.org/merged ascii           contrib main non-free
deb http://deb.devuan.org/merged ascii-updates   contrib main non-free
deb http://deb.devuan.org/merged ascii-security  contrib main non-free
deb http://deb.devuan.org/merged ascii-backports contrib main non-free

Well, this is getting weirder. First:

i A linux-image-4.9.0-11-amd64 - Linux 4.9 for 64-bit PCs
i A linux-image-4.9.0-6-amd64 - Linux 4.9 for 64-bit PCs
i A linux-image-4.9.0-9-amd64 - Linux 4.9 for 64-bit PCs
i  linux-image-amd64 - Linux for 64-bit PCs (meta-package)

There are THREE images showing as installed, besides the meta-package. But beyond that, I checked for new updates again and there is ANOTHER linux-image available for my machine. Maybe this is a correction for the mistake that resulted in multiple install entries?

The adventure continues. Unbelievably, I've got DNS-over-TLS working on Windows before Linux. But, there are nice example configs posted to the Unbound support mailing list... And *ix stuff is always more difficult to figure out.

But I got a surprise when I installed dnssec-trigger on one of my Linux test systems and then tried to test it. It seems that nslookup and dig are not installed by default anymore? If they are associated with bind (as part of bind-tools) could installing unbound have removed them? Would it possibly interfere with unbound to (re)install these bind-utils? Or will they work the same with unbound as they do with bind?

Wow! That's good to know! I will definitely keep an eye on that.

The Slashdot article also has a post from someone pointing out an alternative called Claws Mail. https://www.claws-mail.org/

So there are a few options. But I still hope that the current Thunderbird is adopted by someone before it is ruined.

Well, this is annoying. Stubby is apparently only in Ceres/Beowulf, not the current Ascii release. And of course not in Windows at all.  I was hoping to learn something useful on both Linux and Windows by using unbound in both systems. Looks like I might need to find independent solutions. At least the unbound package from nlnet labs does implement DNSSEC validation in Windows, which is better than the default of accepting the packet but not really checking it.

What I really need, though, is DNS-over-TLS for Linux laptops that does not use DHCP supplied servers. The dnssec-trigger package uses DHCP to get the servers, which is OK for desktops at home but not laptops in public places. I think it can be done with unbound, but I'm going to have to read a lot of documentation. Or maybe I'll just have to wait until Beowulf is officially released and stable.

After fiddling with dnssec-trigger in Linux and the unbound installer for Windows, all I can say is both seem to install OK and do whatever their default setting tells them to. But I can't tell if they are doing DNS-over-TLS and don't see any information about how to configure either to use it.

Unetbootin is not the only bootable USB creator. As far as I know, Rufus can install multiple environments on a single USB stick. But I've never used it that way myself.

https://rufus.ie/

This is a much older system, and I've not gotten to the point of setting up any VMs yet. But who knows, there could be a relationship between the problems since they are so similar.

Just today I've gotten MX Linux 18.3 setup on this system that was having the problems. Now I just need to run it for a while and see if something similar happens. And I'll be installing Devuan Ascii on some other newer systems soon.

Now I am wondering if I ought to open a completely different thread. Before resorting to trying a completely different distro to escape the random freezing problem, I decided to experiment with enabling swap. Since modern computers always have plenty of RAM, at least for ordinary desktop use, I have tended to skip the swap partition and just run any Linux without swap at all. But when I edited a swap partition into my Devuan test system and enabled it, things seem to work much better. Haven't had the time to test extensively yet, but it seems to have run for a whole afternoon without any freezing. This seems bizarre, since I've never come close to filling the RAM on this machine, so I don't see how swap would make any difference. But as I have searched around other forums, the discussions (which can get very technical about kernel issues) seem to say that swap is very deeply embedded in how the kernel works and you ought to have at least a token swap partition on any system.

Well, the online database for the Debian repositories says there is a powstatd for CyberPower UPses. But it doesn't show up when searching with aptitude. On the other hand, the xfce "power manager" is installed by default. It does pop up a message soon after booting about noticing my UPS and that it is charged, but that quickly disappears. How do I get a widget to stay on the task bar where I can check it? There doesn't seem to be anything in the power manager preferences, but there is something or other that keeps a status icon on the task bar in Mint.

Yeah, I found that in the repositories. But for some reason it's accessed through a metapackage named ups-monitor and simply putting that name on the command line causes aptitude to complain and refuse to install it. There are two packages, apcupsd and nut-client, and I have to "choose" one. Not sure what that means with a metapackage. Additional command line arguments?

After the freeze problem hit again, I realized I would have to try different hardware. The test system is ~12-year-old hardware. If not for the huge amount of kernel modifications for the Spectre and Meltdown panic, I bet it would still work fine. But things have changed and some hardware is just going obsolete.

The next system is "only" ~5-year-old hardware. A Haswell generation CPU on an Asus motherboard rather than the ancient nForce. Since it is a completely different system, there might be other problems. But I'll be watching for the video freeze problem and report if this occurs again. What concerns me is some of my other systems are older than this, though not as old as the first test system. I hope they are still compatible with all these kernel tweaks.