Yup, either singular or plural. It’s clear from context because you always refer to them in a previous clause. The user did this, they… The class did this, they…

The user must do this before first use, if he or she fails to… Ugh

The user must do this before first use, if they fail to…😘👌

They has been used like this for a long, long time.

And what are all the other definitions? Words can have more than one, like “they” does.