Before I update using the amazing upgrade tool to Crimson (all foreign pkgs removed or downgraded!), I have a concern about “no longer required packages” that I have abstained from removing, for fear of screwing something up. Should I
apt-get autoremove
all of the “no longer required” pkgs? Or, will the upgrade obviate the need to do this?
You should list here what packages apt autoremove proposes to remove.
here goes:
Reading state information... Done
The following packages were automatically installed and are no longer required:
apache2-bin fonts-linuxlibertine gir1.2-champlain-0.12 gir1.2-clutter-1.0 gir1.2-cogl-1.0 gir1.2-coglpango-1.0
gir1.2-geocodeglib-1.0 gir1.2-gfbgraph-0.2 gir1.2-goa-1.0 gir1.2-gtkchamplain-0.12 gir1.2-gtkclutter-1.0
gir1.2-rest-0.7 gir1.2-wnck-3.0 haveged libapr1 libaprutil1 libaprutil1-dbd-sqlite3 libaprutil1-ldap libavahi-core7
libchamplain-0.12-0 libchamplain-gtk-0.12-0 libdaemon0 libges-1.0-0 libgovirt-common libgovirt2 libhavege2
libjim0.79 libmbim-glib4 libmbim-proxy libopengl0 libpcre2-32-0 libqmi-glib5 libqmi-proxy libwnck-3-0
libwnck-3-common libwpe-1.0-1 libwpebackend-fdo-1.0-1 libxres1 linux-headers-5.10.0-11-amd64
linux-headers-5.10.0-11-common linux-headers-5.10.0-42-amd64 linux-headers-5.10.0-42-common
linux-image-5.10.0-11-amd64 perl-tk python3-louis python3-pyatspi python3-speechd usb-modeswitch
usb-modeswitch-data xkbset
I have removed the un-needed linux images/headers…And haveged seems important…
Yes, whenever apt autoremove offers to remove a kernel, you should at a minimum ensure that it is not the running version (uname -r). 
Other than the kernels, I didn’t see anything of concern.
Bear in mind that packages whose name contains a version may have been superseded by a similarly named package with a higher version in the package name.
Of course, you should always image before a major upgrade (in case the upgrade goes pear-shaped) and preferably image after the upgrade (so that you don’t have to redo the upgrade if something unrelated goes wrong soon afterwards).
As long as the computer still boots after the major upgrade, you can install again anything that you think you need but which has been removed. (Hence you can wonder why it is removing Apache and only you know what you have been doing with Apache, if anything, and whether you need it - but you should be able to install it afterwards if you do actually need it.)
I appreciate the backup advice. PureOS is my first time using gnome, so I figured better safe than sorry. Thank you 
Just FYI:
:~$ uname -r
5.10.0-44-amd64