In this video, I go over 10 things you should do after installing Ubuntu.
This video is mainly focused on Ubuntu, but most of these will apply to other distros as well.

Timestamps:
0:00 Introduction
0:45 10. Install Updates
1:44 9. Disable "Problem Reporting"
2:04 8. Enable "Automatically Delete Temporary Files"
2:34 7. Enable The Firewall
3:35 6. Encrypt Your Home Folder
If you're wondering how to do that, I made a video showing you how. Click the link below to watch:
https://youtu.be/cUu3qJnXWaA
4:00 5. Install GNOME Tweaks
5:25 4. Enable "Night Light"
6:10 3. Install GNOME Software
8:51 2. Install Flatpak
If you're wondering how to do that, click the link below for the official guide telling you how:
https://flatpak.org/setup/Ubuntu/
10:51 1. Install Some Apps
11:21 Bonus: Try The Dark Mode
12:12 Conclusion