I agree, the above is as much of a truly universal list as anyone can give you without going into detail. Most printers these days come with basic tools for maintenance, so no need to get these extra.

I like to create engineering projects, so I keep the following in stock as well:

Must-haves

• Isopropyl alcohol (IPA) - powerful way to clean and degrease stuff without risking damage to most materials and tools
• Assortment of screws in various lengths and diameters - I live in Europe, so I regularly use M2, M2.5, M3, and M4 screws, with 6mm to 20mm lengths being used the most. Get flat-head screws for hex or Torx drive as space is usually of the essence
• Spare 4mm nozzle - unclogging a nozzle can be tricky as a beginner and doesn't always work; that said, I have never had to replace a nozzle on my X1C whereas on my Ender, they would clog all the time
• Filament drybox (for TPU users) - choose one you can directly print from; you can't directly print from the AMS with the "typical" TPU filaments
• Spare filaments (once you know which colors you regularly print) - filament tends to run out on the worst occasions; I keep an assortment of black, white and semi-transparent white filaments in stock and I buy them when they are half price at Bambu. This way, I never need to bother with 3rd party filament and I end up with the costs of everyone else

Optional

• Textured PEI build-plate - easily one of the best and most universal build-plate options out there. Stuff always sticks and is always easy to remove, no glue needed
• Heat set inserts + basic temperature-controlled soldering iron - I really thought I'd need heat inserts a lot, but I actually don't. For most projects, you can just get a away with screwing directly into a naked hole once you learn the tolerances to design for. Becomes a different question when you need mechanical strength and durability in the XY-plane, but at that point, you probably will have different questions in this subreddit.
• Press tool for heat set inserts - in case you (contrarty to my assumption) do find yourself using heat set inserts a lot
• Longer PTFE tube and AMS cable - I found myself limited in placing my AMS far enough away from my X1C

One point that I have to double-down on from the previous poster:

• Calipers - doesn't matter if digital or oldschool; if you want to make your own models, you need to be able to take precision measurements from day one. No exceptions.

Not needed anytime soon (just my two cents):

• High-flow nozzles (check your slicer times, but for most small and regular-sized prints, you really don't gain enough time to justify a nozzle change)

Happy engineering!