Install ubuntu plymouth with oem logo:
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For ubuntu 20.04+

1. Install plymouth-theme-spinner.
sudo apt install plymouth-theme-spinner
This is the OEM Boot logo theme


2. Update alternatives for Plymouth
sudo update-alternatives --config default.plymouth
It'll let you pick a default theme if more than one are installed.
Select the /usr/share/plymouth/themes/bgrt/bgrt.plymouth theme.

3. Finally run
sudo update-initramfs -u

And reboot.


For ubuntu 18.04:
You need to add a few setps from the previus since it is not offcally suported:

Before step 1, add this to yyour /etc/fstab:
deb http://mirror.cs.uwaterloo.ca/ubuntu/ focal main

Save, then
sudo apt update
*DO NOT UPGRADE!* can breck system,
Then folow step 1.
When step one is finshed, go back to your fstab, remove or comment out the line just added, then run "sudo apt update agin"
Then continue on from step 2.


Sources:
https://askubuntu.com/questions/1230257/oem-logo-doesnt-appear-on-startup
Date: November 27th 2021