The first Galaxy S21 disassembly video has arrived on YouTube, courtesy of the channel P3K. It suggests that repairing this base-model smartphone might not be too difficult, even though Samsung makes it look that way with its new rear panel. The device's thermal management system is also on show in this post.
https://www.notebookcheck.net/An-initial-Samsung-Galaxy-S21-teardown-hints-at-the-future-of-reparability-for-its-new-flagship-series.515764.0.html