Yes I'd like to see the log file from startx down to that switch back to VT4.

The command you are using,

git rev-list --all | xargs git grep -F python2.7

scans all versions of all files in reverse chronological order, to find "python2.7".

Probably you mean to only check the latest version of the files? Like

grep  -F python2.7 -r *

which would not report any match.

Note that cups-browsed is only used for publishing the printers of your machine for use by other machines. It has nothing to do with how your machine connects to the printers.

You really don't need cups-browsed at all. (One might possibly be able to draw up some use case where it could be close to useful, even if still not necessary). Just purge it.

Do you use emacs to edit files? Does emacs leave backup files? How are they named? Have you edited /etc/init.d/connman with emacs? Are you wasting space here?

When you go multiarch, you also need to apt-get update and apt-get upgrade; "update" is for updating the local meta files about packages, and "upgrade" is for loading the packages supporting the new architecture.

There's good detail at https://wiki.debian.org/Multiarch/HOWTO

ethtool -P wlan0 might show something, probably the working address though.

mmm then maybe it's the opposite way; that the firmware loads with some random default mac, and this eventually gets updated from the hardware. If so I suppose a binary scan of the firmware could possibly find that first mac...

When you say "no network manager at all" you actually mean "just using ifupdown". That is the traditional network management which is configured by means of a text editor to edit its configuration files... It is indeed the simplest and easiest way with maximal flexibility.

Given that your /etc/resolv.conf is a link it suggests you also have the package resolvconf installed, and that would provide an additional depth to the confusion.

But in any case, DNS setting is part of the DHCP protocol; you know, when your machine contacts the router so as to get an IP address. At that time your machine is also told the IP address of the outbound gateway and the address of the DNS server(s). Those are suggestions by the DHCP server (your router) which get digested by the DHCP client running on your machine. The IP address is assigned to the network interface (via a kernel system call); the gateway IP is assigned to the routing table (via another kernel system call), and the DNS IP address(es) is registered in the file /etc/resolv.conf.

All that happens regardless of which networking software you use; whether it's plain ifupdown, wicd, network-manager or connman.. or whatever.

With resolvconf, you (unbeknowingly?) have opted for a local control of /etc/resolv.conf which is at odds with most networking software unless it also is configured to avoid messing with /etc/resolv.conf. Your first step towards bliss would be to purge resolvconf and reinstate /etc/resolv.conf as a text file.

Yes apt-get update does that. The downloaded "packages" files are kept in /var/lib/apt/lists

It was FUD whether you accept it or not. Sometimes a couple of thoughts before typing can do wonders.

Yes, wicd did/does provide a good and fairly distinct GUI for configuring the network devices and before it was abandoned due to the python2 -> python3 change it was still only in the beginning of its path to enshittification, so quite a good option if one feels a need for a GUI.