Comment 6 for bug 1874283

I installed the official release of ubuntu mate 20.04 and faced this problem. I think I managed to identify it more accurately. This is how it looked in my case:
After recording the ISO image on a USB flash drive, I booted the system in BIOS emulation mode (the boot mode is important here because if you boot in efi mode there is no problem).
After the welcoming sound I pressed the key combination Super + ALT + s.
In my case the Orca turned on, but I could not do anything, because clicking on the cursor arrows and the tab key did not give any result (Orca simply pronounces the name of the pressed key, but does not tell where the cursor is).
Important notes: 1. With the help of a sighted assistant I found out that if you run the installer from the screen that appears when loading, the installer is not accessible for Orca. Ubuntu 19.10 had no such problem. The whole dialog that appears before loading the live system is not available; 2. If you boot the system into live mode and run the installer, then for Orca it will also be not available.
To fix the situation you need to enable support for assistive technologies and change the user session. after that the installer becomes available and a blind user can install the system on his own.
There are no problems described above, if you boot the system in EFI mode.

I would be very grateful if you help solve these problems. The current situation complicates the installation of Ubuntu 20.04 for those blind users who, for one reason or another, use BIOS emulation rather than EFI.