I recently had to set up Ubuntu 19.10 on a friend's laptop with a dead keyboard so had to use the on-screen keyboard. For some reason the keyboard wouldn't show up in the installer's text fields so no way to enter username, password, etc. It works everywhere else, but not in the installer, presumably because it's using the wrong toolkit out of the dozens of GUI toolkits available and the rest of the desktop doesn't recognise its text fields properly.

So unfortunately I still have to agree - how come the built-in installer program not play ball with the built-in accessibility features, and why wasn't this tested?

Logging in with the OSK also had a quirk - if you request the OSK on the login screen, common sense would suggest that you also want the OSK to persist once you're logged in... but no - once logged in you have to manually go in settings and enable it again. This is not a big deal, but just having someone think about the UX would've taken care of this.

Finally getting Netflix to work was annoying; Firefox is actually nice enough to let me know that the page requires DRM content and offered to enable it in one click without arguing about licenses or non-free software, but it still didn't work... after searching around it seems like I had to enable the non-free repo and install an extra "libavcodec" package. I figured it out, but I wouldn't blame a casual user if they gave up and said "Linux sucks".