Some people have reported problems installing Mastodon v2.8.1 due to gem compilation.

This and a few other small bugs have been fixed in #Mastodon v2.8.2:

https://github.com/tootsuite/mastodon/releases/tag/v2.8.2

Improving support for adult content on Mastodon: Introducing Blurhash in Mastodon 2.8.1

https://blog.joinmastodon.org/2019/05/improving-support-for-adult-content-on-mastodon/