I have files from the late 1980's that I can still read, but only with Libre Office because Apple's supplied apps can't read old MacWrite files.
Some people swear by OneNote or Notion or Keep or various mind mapping software, but keeping things cross platform and simple is a challenge. I was never an Evernote person, but it sounds like that turned into a bit of a debacle. These tools work for now, but will they work 5 or 10 years from now?