macOS Mojave dynamic background re-implement as GTK+ background slideshow. Background images are changed to reflect the time of the day.

mojave.xml

<!-- Instructions:
- Download and unzip Mojave dynamic background here: https://files.rb.gd/mojave_dynamic.zip 
- Rename the extracted folder as "mojave-background" (Excuse the trouble but I renamed it on my machine and already use that path in the XML file)
- Save this xml file next to the Mojave background files
- Fix the path to the background images below (better using absolute path)
- Lastly, either: 
  + GNOME: Use gnome-tweaks tool to select this XML as wallpaper (as default wallpaper settings won't let you choose wallpaper from custom path)
  + MATE: Go to background setting (in Appearance) > Choose +Add... > make sure **All files** filter is selected at the bottom right > Then choose mojave.xml
-->
<background>
  <starttime>
    <year>2014</year>
    <month>01</month>
    <day>11</day>
    <hour>0</hour>
    <minute>00</minute>
    <second>00</second>
  </starttime>
  <!-- 00:00 -->
  <static>
    <duration>10795.0</duration>
    <file>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_15.jpeg</file>
  </static>
  <transition type="overlay">
    <duration>5.0</duration>
    <from>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_15.jpeg</from>
    <to>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_16.jpeg</to>
  </transition>
  <!-- 03:00 -->
  <static>
    <duration>10795.0</duration>
    <file>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_16.jpeg</file>
  </static>
  <transition type="overlay">
    <duration>5.0</duration>
    <from>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_16.jpeg</from>
    <to>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_1.jpeg</to>
  </transition>
  <!-- 05:00 -->
  <static>
    <duration>3595.0</duration>
    <file>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_1.jpeg</file>
  </static>
  <transition type="overlay">
    <duration>5.0</duration>
    <from>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_1.jpeg</from>
    <to>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_2.jpeg</to>
  </transition>
  <!-- 06:00 -->
  <static>
    <duration>3595.0</duration>
    <file>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_2.jpeg</file>
  </static>
  <transition type="overlay">
    <duration>5.0</duration>
    <from>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_2.jpeg</from>
    <to>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_3.jpeg</to>
  </transition>
  <!-- 07:00 -->
  <static>
    <duration>3595.0</duration>
    <file>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_3.jpeg</file>
  </static>
  <transition type="overlay">
    <duration>5.0</duration>
    <from>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_3.jpeg</from>
    <to>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_4.jpeg</to>
  </transition>
  <!-- 08:00 -->
  <static>
    <duration>3595.0</duration>
    <file>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_4.jpeg</file>
  </static>
  <transition type="overlay">
    <duration>5.0</duration>
    <from>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_4.jpeg</from>
    <to>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_5.jpeg</to>
  </transition>
  <!-- 09:00 -->
  <static>
    <duration>3595.0</duration>
    <file>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_5.jpeg</file>
  </static>
  <transition type="overlay">
    <duration>5.0</duration>
    <from>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_5.jpeg</from>
    <to>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_6.jpeg</to>
  </transition>
  <!-- 10:00 -->
  <static>
    <duration>3595.0</duration>
    <file>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_6.jpeg</file>
  </static>
  <transition type="overlay">
    <duration>5.0</duration>
    <from>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_6.jpeg</from>
    <to>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_7.jpeg</to>
  </transition>
  <!-- 11:00 -->
  <static>
    <duration>7195.0</duration>
    <file>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_7.jpeg</file>
  </static>
  <transition type="overlay">
    <duration>5.0</duration>
    <from>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_7.jpeg</from>
    <to>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_8.jpeg</to>
  </transition>
  <!-- 13:00 -->
  <static>
    <duration>3595.0</duration>
    <file>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_8.jpeg</file>
  </static>
  <transition type="overlay">
    <duration>5.0</duration>
    <from>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_8.jpeg</from>
    <to>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_9.jpeg</to>
  </transition>
  <!-- 14:00 -->
  <static>
    <duration>3595.0</duration>
    <file>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_9.jpeg</file>
  </static>
  <transition type="overlay">
    <duration>5.0</duration>
    <from>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_9.jpeg</from>
    <to>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_10.jpeg</to>
  </transition>
  <!-- 15:00 -->
  <static>
    <duration>3595.0</duration>
    <file>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_10.jpeg</file>
  </static>
  <transition type="overlay">
    <duration>5.0</duration>
    <from>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_10.jpeg</from>
    <to>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_11.jpeg</to>
  </transition>
  <!-- 16:00 -->
  <static>
    <duration>3595.0</duration>
    <file>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_11.jpeg</file>
  </static>
  <transition type="overlay">
    <duration>5.0</duration>
    <from>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_11.jpeg</from>
    <to>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_12.jpeg</to>
  </transition>
  <!-- 17:00 -->
  <static>
    <duration>3595.0</duration>
    <file>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_12.jpeg</file>
  </static>
  <transition type="overlay">
    <duration>5.0</duration>
    <from>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_12.jpeg</from>
    <to>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_13.jpeg</to>
  </transition>
  <!-- 18:00 -->
  <static>
    <duration>7195.0</duration>
    <file>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_13.jpeg</file>
  </static>
  <transition type="overlay">
    <duration>5.0</duration>
    <from>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_13.jpeg</from>
    <to>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_14.jpeg</to>
  </transition>
  <!-- 20:00 -->
  <static>
    <duration>10795.0</duration>
    <file>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_14.jpeg</file>
  </static>
  <transition type="overlay">
    <duration>5.0</duration>
    <from>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_14.jpeg</from>
    <to>/home/thanh/Pictures/wallpapers/mojave-background/mojave_dynamic_15.jpeg</to>
  </transition>
</background>

Anyone else having issues with smooth transitions? I'm on Ubuntu 20.04, and the pictures just abruptly change from one to another.

hello @guvarallo, that's because of short transition time (only 5 sec), I edited this script, and added smooth transition. i will upload that script in my GitHub with bunch of other dynamic wallpapers ( here ). Also everyone can easily modify or make new wallpaper scripts with program called "Dynamic Wallpaper Editor", which is preinstalled on Manjaro gnome edition.