Some Tools for Accessibility (focused on vision)

Screen Readers, When You Can't See the Screen

The Wikipedia article on Screen Readers does a nice job explaining screen readers.
Windows - NVDA by NVAccess (open source), JAWS by Freedom Scientific (commercial), Narrator by Microsoft (included with the OS)
Linux - Orca from GNOME, I use Linux on WSL2 and have no experience with Orca.
MacOS - VoiceOver on MacOS build in to OS, (I think) the only option for MacOS.
Android - TalkBack on Android, native on Android devices though not guaranteed on vendor devices using Android.
iOS - VoiceOver on iOS, works across many devices.

People with some vision might use a screen magnifier to enlarge portions of their screen.
The screen magnifier article on Wikipedia has some high level info on magnifiers including links to specifics.
Mobile platforms generally support the ability to zoom in/out. that functionality can be disabled by an app. Don't disable zoom in your mobile apps! :)