Have you disabled the Secure Boot?I guess the secure boot caused that.

Maybe you should try UEFI,and use the tools named Ventoy.I never meet such problems,humm...If my reply can't help you, you probably looking for helping on your PC maker's website.And try to google it.(I am so sorry if my poor English mislead you something wrong.)

I am sorry to hear that,and this problem have overed my ability to work out.Hummm...What's equipment do you have?

A choice is you can question your PC maker for help.

As far as I know,the forum of Chinese version is active,you may get some help on it.

Now I have forwared your problem on forum of Chinese version.The following link is it.

https://bbs.deepin.org/post/255557

I suspect it's related to the secure boot option or fast boot option in the BIOS setting. Try disable them and see if it helps with your case. I had similar issue when switiching from Windows to Deepin the first time.

And as for the installation process, instead of RUFUS you could try Ventory: https://www.ventoy.net/en/

This should be handy. It will partition your thumbdrive into a EFI section and a normal one. Then just copy the OS iso file into the normal section, which should be the only one visible by default. Basically, you could use ventory to load any OS iso files. It will present all the options during booting.

And don't forget to check md5,too.

I usually install easyuefi on Windows,then add deepin boot entry with easyuefi.

Finally move deepin to the 1st line,reboot and you can see the menu to selec OS.

good luck~