I’m glad to hear that people are moving away from Adobe’s malicious reader. For the record, Sumatra is a good reader for Windows, xReader (part of the Linux Mint team’s “XApps” initiative) is good for GNU/Linux, Document Viewer is good for Android, and MuPDF is good for all of the above (and a few other Unix-like systems, including MacOS X, I believe), although it is quite bare bones.
Also, Firefox, Chrome/Chromium, Brave, and most likely several other browsers have built-in PDF viewers, and can be used as a substitute for a standalone viewer. However, browsers that use PDF.js (Brave, Firefox) generally aren’t the best when it comes to PDF viewing (the process is slow, and the results poorly rendered, and thus making documents hard to read). However, the viewer built into Chrome/Chromium is quite fast and renders quite nicely.