Next you are obviously entering a software maintenance mode which involves fixing "bugs" in the software to adapt it to the current X11 environment, and that's not something I want to commit to be involved in. I see there is a readme file regarding FvwmTaskbar; possibly related.

Good luck.

/usr/local/lib/X11/fvwm95/XClassTaskbar

not found

DEFAULT_SESSION=startfvwm95

case $1 in

lxqt)
exec startlxqt
;;

xfce4)
exec startxfce4
;;

mate)
exec startmate
;;

fvwm95|*)
exec startfvwm95
;;

#exec $DEFAULT_SESSION
#;;

esac

Nothing is happened. After reboot or change session, Slim not enter to fvwm95, Slim sty at login screen.

xfce4|*)

???
So the second option is that "if the argument $1 matches xfce4 or matches * (aka anything), then use startxfce4". That makes the remaining ones mere decoration.

For sure you meant them to be in a different order.

But how now i can use it? When i do logout and press F1 on login Slim screen i do not see FVWM96 session.

Here my /home/freeartist/.xinitrc                                                                                                                                           

DEFAULT_SESSION=startxfce4

case $1 in

lxqt)
exec startlxqt
;;

xfce4|*)
exec startxfce4
;;

mate)
exec startmate
;;

fvwm95)
exec startfvwm95
;;

#exec $DEFAULT_SESSION
#;;

esac

E.g, first error in LOG says

/usr/local/include/X11/Xlib.h:5:8: error: unknown type name ‘XFontStruct’

which is odd since XFontStruct is defined in /usr/include/XLib.h (line 1052) from libx11-dev=2:1.7.5-1

Therefore I'm guessing you have some remnants from trials/experimentations in /usr/local/include

EDIT: Thought to mention:

• I downloaded fvwm95-2.0.43f.tar.gz and unpacked that into /usr/local/src/fvwm95-2.0.43f/ for building

• ran ./configure, then make repeatedly while dealing with its errors, resulting in pulling in those libraries and some minor edits to:

  1. modules/FvwmIconMan/FvwmIconMan.c

  2. modules/FvwmScroll/GrabWindow.c

  3. modules/FvwmTaskBar/Goodies.c

With that it compiles (with lots of warnings) for me, and I don't know how well it runs.

root@devuan:/usr/local/src/fvwm95---#  apt-get install libx11-dev libxpm-dev libxext-dev libxt-dev xbitmaps libxmu-headers
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
libx11-dev is already the newest version (2:1.7.5-1).
libxext-dev is already the newest version (2:1.3.4-1).
libxmu-headers is already the newest version (2:1.1.3-3).
libxpm-dev is already the newest version (1:3.5.12-1).
libxt-dev is already the newest version (1:1.2.1-1).
xbitmaps is already the newest version (1.1.1-2.1).
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
root@devuan:/usr/local/src/fvwm95---# 

Here logs.
https://drive.google.com/drive/folders/ … sp=sharing

In this case you will need to find the "error: ..." lines to figure out what the main problems are. All the warnings should really be tended to as well, but they doesn't stop the compilation.

I mostly got missing include files and needed to install:

# apt-get install libx11-dev libxpm-dev libxext-dev libxt-dev xbitmaps libxmu-headers

plus a light manual touch to remove some misplaced "##", and

now it looks like the link recipe of the Makefile needs polishing as well.

https://streamable.com/v84307

and installed dependencies packages txt
 
https://pastebin.com/raw/iWcVZach