I've been working on some stuff lately for my wife's 92 year old friend she looks after, using bigger print and simpler interfaces for older eyes.

unfortunately it does not support RSS plugin (as does claws-mail), but your probably would not mind;
(it needs some adaptation for gmail to function if 2FA is active, though)

congratulations for having such a "modern" and lively father

If you want to change your dad's system, rather give him an additional system, like an ultra fine resolution laptop from Apple. Any Apple lappy from the last ten years will do.  The reason I suggest Apple is that they are very good for people with failing eyesight.  As you get older you have more and more junk floating in your eyes and dim spots etc. and your short term memory gets bad, which makes it super annoying when a UI suddenly changes.  Maybe in a few weeks you will see him using the new one only and then you can recycle the old one.

I had cancer and the treatment affected my memory in subtle ways for a year or so and it recently started to recover, so I have much sympathy for old geezers now!

is it possible that libgtk3-nocsd0 would help?

Maybe. Here's some relevant info that may be helpful:

How do I disable client side decoration globally in GNOME?
https://askubuntu.com/questions/961161/ … y-in-gnome

gtk3-nocsd - transparently disable Gtk+3 client side decorations (CSD)
https://manpages.ubuntu.com/manpages/no … csd.1.html

This change to Evolution was also discussed in this article:

Evolution Email Client Now Uses a Headerbar/CSD
https://www.omgubuntu.co.uk/2022/09/evo … header-bar

The first comment shown in the comments section offers a potential solution.

EDIT:

If gsettings is not installed, install libglib2.0-bin.

For example:

# aptitude install libglib2.0-bin

Back from sport to PC: What does your father with his PC? One target is clear, we did read it: email correspondence. Ok, but what else?

Decades ago, a developer staff did design an OS especially for old person. It was a kind of mini Puppy Linux based on Ubuntu (with which it was 100 % compatible) so there was no limit (excepted the limits of the beginning Ubuntu itself! It did really have limits...).

The base did propose only a hand of activity:

- browse the web and electronic mail
- calculate
- write
- listen music
- skype (no distro at this stage of evolution without skype)!

With your continuous experience (my did finish, concerning old people excepted myself, with the dead of my own father) what would you do change in that definition?

There is no way to avoid this Windows style decoration in Evolution on Daedalus. Stay on Beowulf or at the most upgrade to Chimaera.

is it possible that libgtk3-nocsd0 would help?

apt show libgtk3-nocsd0

Package: libgtk3-nocsd0
Version: 3-1
Priority: optional
Section: libs
Source: gtk3-nocsd
Maintainer: Christian Seiler <christian@iwakd.de>
Installed-Size: 49.2 kB
Depends: libc6 (>= 2.4)
Homepage: https://github.com/PCMan/gtk3-nocsd
Tag: role::shared-lib
Download-Size: 14.5 kB
APT-Sources: http://deb.devuan.org/merged beowulf/main amd64 Packages
Description: Library to disable Gtk+ 3 client side decorations (CSD)
 libgtk3-nocsd is a small LD_PRELOADable library used to disable the
 client side decorations (CSD) of Gtk+ 3.
 .
 Since Gtk+ 3.10, its developers added a so-called header bar or custom
 title bar. With this and the client-side decoration, the original
 title bar and window border provided by the window manager are
 disabled by Gtk+. This makes all Gtk+ 3 programs look like alike, but
 have different handling from other windows on non-GNOME desktops. Even
 worse, this may break some window manager or compositors.
 .
 Unfortunately, there is no reliable way of turning off CSDs in Gtk+
 directly. This library makes this possible.

also found this webpage(for i386? stuff):
ttps://packages.debian.org/buster/i386/libs/libgtk3-nocsd0

judging from the information at this webpage it doesn't solve the header bar issue:
ttps://github.com/PCMan/gtk3-nocsd

making this post more for documentation than any sort of resolution...sigh...still looking and hoping.

It is an undeniable trait of humanity the failure to acknowledge that the days of each one of us are indeed numbered.

Eons go by and it remains the same, unchanged.
Literature of all kinds, from all ages, civilizations and beliefs attest to that.

So worry not and enjoy+thank life for the wonderful gift you have been bestowed.

Merry [fill in] and a Happy [fill in] for you and your father.

Best,

A.

again, heartfelt thanks to all who considered and replied!

Note that to get to Daedalus from Beowulf you have to go through Chimaera first and that might be a good place to hang for a year or two . . .

did a fresh install of Daedalus on a new ssd to leave the Beowulf installation unmolested and so didn't do any "upgrading" but understand your point.