This has nothing to do with Discourse desktop or mobile view as those views control the display and position of the display elements for the application, not the display of post content, as discussed in Give user better info where they are - #19 by musiko).
Tables wrap horizontally because they are embedded in <div class="md-table">, which is controlled by CSS
.md-table {
overflow: y-auto;
}
This should work on any browser on any device, unless something—usually a browser plugin—is interfering with the html (can you run discourse on a private tab in a desktop browser, with all browser plugins disabled).
This should read: large tables with lots of text are not well fitted for mobile, small tables work quite well, here is one example out of many Ajahn Brahmali---Introduction to Pali Offline Course---Wisdom & Wonders 2018