The problem at hand is not about the usability (UI/UX, performance, etc.) of Discord but rather it’s private, closed source for-profit existence being used as a “support” channel for a free and open (source, platform, communication) environment.

I agree with you in principle, but on a pragmatic level, it's very hard to disconnect UI/UX/performance from everything else. I think it's OK to acknowledge that Discord has a weakness when it comes to not being OSS, but a strength when it comes to UX, and I also think it's OK to take advantage of that strength for users that want to do so.

Just to be fully clear, I am never planning to make Discord the main communication channel for lemm.ee announcements, nor to make users feel like it's in any way necessary for them to use Discord just for lemm.ee communications. I am also active on Matrix constantly, and read most of what happens in the Lemmy Matrix channels. Any user that wishes to reach me over Matrix can do so.