Not able to boot into Ubuntu 20.04 alongside Windows 10

You haven’t said what you’ve tried, but I suspect Windows has fast startup enabled - you need to disable that to get grub to load:

In the Windows search bar, enter ‘power and sleep settings’, open it, then select ‘additional power settings’, then ‘choose what the power button does’. You’ll probably have to click ‘change settings that are correctly unavailable’ to deselect ‘turn on fast startup’.

Thanks to ChanganAuto: you’ll also need to open UEFI settings > Boot and change to "Ubuntu"instead.

When you’ve done that, reboot and hopefully grub menu will appear. I hope that helps.