Buildings that have gender-free/gender-neutral restrooms create a physical environment that welcomes and affirms transgender and nonbinary people. If a building already has a single stall bathroom, it is easy to make it gender-free with a new sign. In fact, it's the law.
In 2019, New Mexico legislature passed the “Gender-Free Restroom Act” requiring all single-stall bathrooms to be accessible to people of any gender.
For multi-stall bathrooms, there are many easy and free options to increase safety for transgender people.
See the Unitarian Universalist toolkit and signage resources.
Here is a Restroom Toolkit by the University of Maryland.