my goal is to switch von Devuan jessie to ascii. I had a Devuan installation before with Xfce and MATE and made some experiments with apt-get upgrade and dist-upgrade, but the results were not trustworthy somehow.
So I made a fresh install of Devuan with Xfce today and repeated my dist-upgrade. Here's how I did it:

First, I logged in as normal user, started the terminal (in Xfce Desktop Environment), and switched to root (su).

Second, changed sources.list to use ascii packages:

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

Third, performed

apt-get update
apt-get dist-upgrade

During dist-upgrade already some errors came up:
There were dependency problems with dpkg package (and one or two others) and some folders couldn't be deleted because not empty, these, for example:
- etc/udev/rules.d
- etc/udev
- etc/kbd
- var/lib/initramfs-tools
- ...

Then I wondered why my sources.list has grown by the two following lines I never added myself. What's the difference to pkgmaster and why were these lines added?

# Devuan repositories
deb http://packages.devuan.org/merged/ ascii non-free main  
deb-src http://packages.devuan.org/merged/ ascii non-free main

Then I restarted the system, it successfully started again but I noticed that I cannot start synaptic as my "normal" user anymore (when starting via terminal, it says command not found). It works only in terminal when I switch to root. Maybe some permissions are broken, but why?

Additionally, during the starting process I noticed three situations where the system is idle/hanging (no HDD actions) for several seconds and I don't know what exactly the OS is doing here.
1. While it logs [....] Waiting for /dev to be fully populated...[   16.092224] [drm:drm_atomic_helper_commit_cleanup_done [drm_kms_helper]]
*ERROR* [CRTC:26:pipe A] flip_done timed out the system seems to be idle for about 10 seconds but seems to change the video mode meanwhile.
2. After it logs Starting slim: slim system hangs about 10 seconds, then the WLAN LED starts blinking the first time and then the login screen appears. (For testing, I disabled automatic WLAN connection and after restart I had the same idle time, so WLAN doesn't cause the problem here)
3. After logging in, the desktop background appears and, the system seems to hang (no hdd) for about 5 seconds, the mouse cursor appears and then the system is idle again for 15 seconds! After that the all desktop elements like taskbar and icons are drawn.

Summarized, the starting process takes about 30 seconds longer than before the dist-upgrade due to the idle times.
[Edit: Searched the internet and checked dmesg. The idle times seem to be caused by a kernel bug. Have kernel 4.9.0-5-amd64 now, had probably 3.x before]

That was much of text now and I don't expect a solution for everything now, but appreciate your support even if it only helps to solve one thing...
Thanks!