The open source client doesn't mean jack shit dude.
Telegram also has open source client.
Your data lives on their servers not clients and also, even if the server code is open source, there are many ways for a backdoor and violations of privacy in the infrastructure. When you give up your phone number, there is no privacy.
They are super shady, blocked some important security researchers that found a vulnerability from them on all platforms, and they offer no explanation on why using a phone number is MANDATORY for signup.
Just search IBM IoT and look at IBM acquisitions in the last decade.
Everyone "used to work for that company" on the internet. And even if you used to work there it doesn't mean you know anything about their business.
IBM is more of a Holding now. Like Volkswagen. Just because someone works at audi it doesn't mean they know anything about Lamborghini.
SystemD works great, but the corporations and politics behind it will ruin Linux if they fully take over.
They are already optimizing heavily for IoT just because IBM is heavily focused on IoT
Don't focus too much on tools (languages,ide, editor, etc.)
Get strong fundamentals in math and software, code with C and a high level language like python for a couple of years and you're good on the tooling side.
Focus on your mathematics, logic and philosophy. These are what separate legendary engineers, scientists and visionaries from people who are only amazing at programming.
Remember that you are an engineer/scientist/philosopher not a cog in the machine that gets told what code to write and writes it.
I highly recommend reading the works of Feynman, Dijkstra, Turing and other greats to better see how they think and approach things.
(Maybe these aren't the direct answers to your questions, but wisdom. damn I wish someone told these stuff to me sooner)
Im using xfce and i3wm.