Makes me realize how much I hate Jira. GitHub now covers a lot of Jira's functionality, Confluence to an extent also.
No it doesn't. Github Issues/Projects replicates about 10% of Jira.
Maybe basic issue tracking is fine for your use case. But if you have multiple teams or need to do planning across longer time horizons e.g. SAFE then this is where Jira comes into its own.
without using a vendor-specific markup format, too!