My next laptop will probably be a Thinkpad T480 from Minifree. But I reckon it will be a while before this one breaks in an irreparable way.

CAD + ML is certainly difficult, maybe that needs a dedicated machine you only use for that? But that will increase costs overall. I’m also not sure how to find PC parts that I know won’t need dedicated firmware. So that part is definitely more tricky, I’m sorry I can’t be more help here :(

As for Matrix and XMPP, I started off with Matrix and found it pretty good for bridging lots of different networks together. But, over time, I came to prefer XMPP for a few reasons:

• Ultimately, I just don’t trust Element, and they do so much of the work. They complain that people are dependent on them and don’t give back, but they were the ones that created this dynamic in the first place. They are a single actor who own the dominant server, clients, and flagship instance, and can really push around the ecosystem in a way that works for them.
• XMPP is more community oriented, no one person can push through changes either at client, server, or server operator level. XMPP is based around extensions and there is an expectation that not every client or server implements every extension. That brings the con of inconsistent experiences, but at the same time, it is much more resilient over the long term (Matrix is now having to deal with the same fragmentation problems that XMPP started experiencing, and building solutions for, 20 years ago).
• XMPP’s network is less centralised, there’s not a mega-server like matrix.org with a lot of power. When matrix.org goes down (which happens semi-regularly), there is a big impact. If a single XMPP server goes down, it doesn’t cause nearly as big a problem. And, there aren’t those mega-instances with scaling problems, so the servers don’t go down as frequently anyway.
• XMPP evolves more slowly and gracefully IMO, as it is already more established (might be a con depending on your worldview). I run debian stable and an update across the Matrix network broke images on my Matrix client. That just doesn’t happen on XMPP, you can lag behind the leading edge for a couple of years and things don’t break even as the network evolves.
• I find XMPP easier to self-host - again subjective, but I could just install prosody via Debian’s archives, and once it was set up, I didn’t have to touch it. I update it with the rest of my server every 2 years, and I don’t fall behind the rest of the network or miss out on much in the meantime. Meanwhile, I have to pay much more attention to my matrix server, I get the software from upstream and not from my distribution, and there are more regular changes that I have to pay attention to.

As for advantages of Matrix:

• They have a flagship client that is available everywhere and has a decent and consistent UX. That name recognition makes it easier to get people to sign up. The XMPP community have done a lot of work to make signups work easily in a decentralised way, and projects like Snikket aim to solve that name recognition and consistency problem, but it is not 100% perfect yet.
• Bridge software to proprietary networks is more actively maintained in Matrix. There is work going on to improve this in XMPP, but I think many in the XMPP community moved focus from bridging to making the first-party experience better.

Many of the pros and cons are based on values (e.g. living on the leading edge vs using something more mature, preferring community based solutions vs commercial ones etc.), so I totally understand and support people who use Matrix instead. Ultimately, both ecosystems can cooperate, learn from each other and are millions of times better than the proprietary networks. That said, above is why I came to prefer XMPP.