Hi @IslandDesign accessibility is huge topic and and is not easy to achieve but if your website has governmental content, full accessibility is mandatory, including optimization for screen reader used by blind people. You can find many articles and books related to this big topic. It can take a few weeks to read, few months to understand and bring it into practice.
If you care only about fonts: adding custom fonts is one of advantages that UX will be identical on any OS on desktop or mobile devices. And again Accessibility aren’t just fonts. As this forum is mainly focused on problems with WF you will be better find more details about your concerns on internet as it is great source of information. Try to use appropriate keywords as eg. “typeface impact on accessibility”.