Can I install ubuntu 20.10 or 20.04LTS on dual boot with windows 10 without USB Drive?

20.04 is a LTS version, i.e. Long Term Support -> 3 or 5 years support --> more stable

20.10 is a more recent version

I'd recommend using 20.04

There seem to be ways to install linux without usb drive - I have never tried them My main recommendation is to make a good backup of your PC before you start even if you do it with a usb-drive ! Any issues with your install without a backup and you'll have an unusable PC.

https://linuxnetmag.com/how-to-install-linux-without-usb/

the site says the following

Using UNetbootin to install Linux in your PC directly from the hard drive.

First download UNetbootin from http://unetbootin.github.io/.

Then, download ISO image for the Linux distributions or flavors supported by UNetbootin.

Next, you have to launch UNetbootin and choose Diskimage, select ISO, and then browse through to pick the ISO image file for the Linux.

Choose Hard Disk for Type, C: for Drive and then you click on the OK button

This will copy files from the selected ISO image straight to your hard drive, add a bootloader to your hard drive, and then you will see an “installation complete” message displayed.

Now after you reboot your Windows PC, it will show a UNetbootin boot entry. You can choose this new entry to boot into the Linux OS and finish installing Linux on your hard drive. Make sure you choose to install it alongside Windows and do not overwrite the Windows partition.

Once the installation is finished, it will reboot into the installed version of Linux through Grub. You can use these instructions for adding Windows to Grub menu after installing Ubuntu or Debian based Linux distributions.

Once Linux has been installed, you can boot back in Windows and launch UNetbootin one more time to delete UNetbootin from your system.