If your free software communications can only be done thru US-based, proprietary options, then you are not free software. To think open source is ideal for your project, but not the tools surrounding it misses the point of trying uplift support & usage of these free sorts of projects (& this isn’t even starting with the privacy & lock-in concerns). Instead of coding around flaws in Microsoft GitHub or building Discord/Slack/Telegram bots, actually build & upstream integrations into the free options as you would like to see folks do unto your own project. Not saying you can’t have these services as an alternative, but as the only option (or the primary option to IIABH) should be shamed & definitely not considered the norm.
Also Matrix is pretty shit, where all the clients/servers run too heavy, & eventual-consistency means self-hosting storage often ballots into ‘too expensive’ which has led to de facto centralization the project cannot fix by design. Meaning Matrix is a better, but still bad chat option.