The same OAuth client can be used for both Confluence and Jira. Depending on what you need to access, a significant limitation to OAuth is that Jira Software APIs (like boards, sprints, and development information) are not covered by 3LO. All of Jira Service Management is fine for the same client.
Trello provides one OAuth strategy. Bitbucket has yet another OAuth implementation so it requires a different client identification (from both Trello and Jira/Confluence). Statuspage and Opsgenie each have their own implementation of API tokens/keys so one client for each.
5 different sets of credentials to manage on your side. 3 different OAuth implementations with slightly different quirks, and 2 different kinds of API tokens with different authorization headers. If only we had some JWT to throw into the mix somewhere? (Seriously, some of those do use JWT inside of OAuth). When you finish, you’ll be an API security expert!