@elb indeed! Maybe switch to weechat with the python modules for slack and element, both of those have worked quite well for me. :)
@elb gomuks is a good TUI Matrix client. I'm not sure about spaces (I only use it for IM), but it does support E2EE. When I want as little resources as possible used, but still get notified if someone messages me and want to be able to reply quickly, I usually use it.
Even for Element I see no point in running the Electron app, why not a Firefox window with Element web app? For me it consumes less than one percent of CPU when not focused and idle.
@unrznbl