No that page was about someone that coould boot from usb but their paticular usb wouldnt boot.  It was trying to fix their usb so it would be bootable.  I was able to switch from UEFI to legacy boot and the options to boot from CD or USB came back. Then once Ubuntu is reinstalled I can switch back to UEFI for the faster boots.  Seems to be the only way to fix this.  I checked I have the newest BIOS.  Don't know what else to try.
My Inspiron shipped with Windows 10, but after years of updates it quit working.  It would crash on boot up. I tried reinstalling fresh but as soon as I update, which is manditory, the system quits working.  I installed with a dual boot of Ubuntu I think the first was 20.04 and it worked great.  But I only had about 200 gig available with Windows taking up most of the hard drive.  I would reinstall every time a new release of Ubuntu came out but only using that portion of the hard drive.  This time, when 21.10 came out I decided that since Windows doesnt work anyway I choose the format entire drive and install fresh option.  Ubuntu works great and now I have the WHOLE 1 TB drive.  But I have noticed I can no longer boot from DVD or USB.  When I hit F12 it only shows ubuntu, Windows boot manager, IPv4, or IPv6 as my options.  I watched plenty of videos and one told me if I enable USB emulation and USB wake that when I reboot and go to the menu I could select USB.  But that didn't work.  Its still just Ubuntu, IPv4, IPv6, and Windows Boot manager.  The only one of any of those that work is the ubuntu.  and no way to boot from either USB or DVD.  Now honestly I am file until April.  As long as nothing goes wrong.  Ubuntu 21.10 seems to be workng great.  But when 22.04 comes out I am going to want to do a clean install and I dont seem to have a way to do that.  Any thoughts?  Thanks.
Dell Inspiron 5755 won't boot from DVD or USB. Boot menu doesnt show either.