Building a threat model helped me figure out what was worth my energy and what can be put off to be done later at my leisure. This should be your first step.
What kind of phone and OS do you use? You can contain the spying a bit if you set up a work profile with Insular or Shelter, install your proprietary apps there, set a schedule for checking those, and turn off the profile otherwise. I realize that it’s not the easiest, but if you can find people to talk to in real life regularly, frequent access to messages / social media need not be a prerequisite to a healthy social life.
Getting hacked through the BIOS/Intel ME, while possible, is statistically highly unlikely, activist or not. If there’s a piece of technology I have to use, but don’t trust, I just keep it at my desk, fine as long as it can’t actively track me moving around. Don’t let perfection get in the way of your bigger goals.
While we’re at it, have you considered libreboot on the T480? A few tiny scraps of the Intel ME do have to be left in place, but realistically they’re not going to see an exploit anytime soon. And you’ll still have most of the satisfaction of liberating your computer.
Cash is pretty accessible where I live, but I’m always in for a surprise when I gravitate towards self-checkout and realize that it’s a card-only machine.
Prepaid cards used to be my go-to online, but it seems that fewer and fewer payment processors are letting them through their “security” checks. They were also next to impossible to obtain when I was in Europe. For a lack of better options on hand, I went with privacy.com’s virtual cards, which doesn’t really anonymize things in the eyes of MasterCard, but I suppose it’s better than nothing.
The only other thing I could think of is signing up for eBay or Amazon with a pseudonym, paying with gift cards purchased at a store with cash, and shipping to a PO box or Amazon pick-up location.
Ideally Monero, but it’s not as straightforward to obtain and there’s a very limited selection of vendors that accept it.