You are right. I should explain it well. Thank you.
First of all I want to tell that my guess was wrong. Bootable Manjaro USB works. I could boot another computer from it.
I am going to explain everything again to give you a clear idea about what happened.
I have Thinkpad E490s laptop. (Core i5-8265U CPU, 8Gb memory, 512GB SSD) Currently, It has Ubuntu 18.04.05 64bit operating system. THE original OS was a Windows 10. Later I installed Ubuntu 18.04 alongside Windows. After a few months, I erased Windows and now it has only Ubuntu 18.04.05. The laptop hard disc has 3 partitions other than Ubuntu installed partition(4 partitions total).
I want to install Manjaro. I made a bootable Manjaro USB, plugged it to my laptop, restarted my laptop, pressed F1, went to the boot order menu, moved the USB to the top, and waited.
Laptop didn’t boot with Manjaro, It came to the grub boot loader of Ubuntu 18.04 and did boot with my existing Ubuntu 18.04. Nothing happened at all due to Manjaro. No error message, nothing unusual compare to a normal TURN ON process of my laptop. Looks like my laptop doesn’t recognize Manjaro USB as a bootable media. That is the problem.
I tried exactly the above process with a bootable Ubuntu 20.04 USB. My laptop did boot with Ubuntu 20.04. It came to the grub boot loader of Ubuntu 20.04 and did boot with Ubuntu 20.04 bootable USB.
Then I guessed my problem as a problem of bootable Manjaro USB and made this question on this forum. I thank everybody for spending valuable time on my problem.
Today morning I tested Manjaro USB with another computer and it did boot that computer with Manjaro. So I conclude, it is not a problem of Manjaro bootable USB. The problem is in between my laptop and Manjaro USB.
I should also say this. I tested this Manjaro USB with another laptop(Thinkpad T14 gen1, windows and Ubuntu 20.04 dual boot) yesterday. That laptop doesn’t have a list to select boot order. I had to select the desired bootable media with the mouse pointer. When I select Manjaro USB, It goes to a totally black screen and quickly goes back to the previous menu(the place where I have to select a bootable media). I clicked Manjaro USB a couple of times. I could not see anything except a totaly black screen. It goes back to the previous menu within a second and let me select a bootble media.
I can summarize my problem as follows,
- My laptop recognizes other Linux bootable USBs (I tested Ubuntu 20.04)
- My Manjaro bootable USB is recognized by another computer
Problem: My laptop doesn’t recognize Manjaro bootable USB