Tried every net solution for days to install linuxcnc

Tried every net solution for days to install linuxcnc, Debian, mint... nothing works. I did get as far as completing the installation successfully a few times, only to have my clean 1TB usb hard drive not be “found” on reboot. Also not showing up in bios “UEFI Boot sources” but the drive is first under bios setup “boot order” The live versions work but not any of the installs. Tried every possible bios setting and disk partition suggestions on the net with no luck. One odd thing that may help find the problem is that “UEFI: IPv4 Realtex PCIe FE family controller” and “UEFI: IPv6 Realtex PCIe FE family controller” keep showing up even after being disabled in “boot order” bios settings. I thought realtex was just for my old HP windows 8 audio system. Even after disabling everything but the USB drive in the boot order bios, the USB drive with the OS is not found. Since the internet came out and after all the OS systems I have installed, Linux OS seems impossible to install. Some Linux user must know what the problem is, but not any I found on the net offering solutions so far have worked.Correction… I misspelled “Realtex” it is “Realtek” 
 

Personally I wouldn't install to a USB drive. Far too many reasons to list.

One thing you have to be absolutely sure is that you are loading the boot loader to the correct USB device.

But if you do want to pursue it, the Debian forums would be the best place to look, as Linuxcnc is just plain old Debian bookworm with a real time kernel and the Linuxcnc app suite installed.

Try a different way

• buy and install a SSD drive
• Download and install Debian Trixie Netinst CD www.debian.org/devel/debian-installer/
• Be sure to select Mate or XFCE desktop 
• in a terminal type:
  • sudo apt update
  • sudo apt install linuxcnc-uspace linuxcnc-uspace-dev

The newer OS should provide better support  for your hardware

For additional tweaking, follow my guide
docs.google.com/document/d/1jeV_4VKzVmOI...diY/edit?usp=sharing

Great suggestions and thanks to all. I am feeling more hopeful already. Since a picture is worth a thousand words, I took some photos of my system, bios options, setting and what I get after a successful installation that can’t be found. I have dedicated this computer to just be a linuxcnc system, so the main hard drive and USB drive were reformatted with FAT before partitioning for a clean start. I used rufus-4.6_x86.exe to prepare a USB boot stick and USB drive with the respective ISOs that worked well for the live but not for installs.

My system.
My bios startup menu.
My UEFI boot options.
My bios boot order.
My bios secure boot configuration options.
And My device not found after a “successful” installation.

Once the live versions were working, I did try a lot of sudo commands in the terminal. Some seemed to work, others said the file could not be found I believe. All things the OS is suppose to include and are required. After all the sudos the system still would not boot to the installed hard drive internal or external USB.

Enable legacy mode.
With internal HDD install grub to /dev/sda.

"I did try a lot of sudo commands in the terminal"
Means nothing and is no help at all trying to fix your issue.

Disable secure boot, probably enable legacy support. Where is your HDD? Perhaps its a legacy device.
Also, let Linux choose the partition type during installation. Its probably EXT4

I will try to list all the sudos and the responses I tried. I gave up on trying to solve the lost install components that were suppose to be in the repositories.

I did try "Disable secure boot, enable legacy" options. I think that may have been the default setting, but I will try anything a few more times just incase it works this time. The internal hard drive was the first thing I tried to install to. but I started using the USB HD because it is newer and I new it was in good shape, also just to try another drive.