AFAIK: E series is bad, kind of trash and not really worth the money (just get something else at the price).

The T and P series are the good ones I think. The X are good also but aren't built to quite the old tank specs of the T and P lines which will last 20 years. They're still a good buy but more care should be taken buying them used compared to T and P which will tend to just work even used. Thinkpads are renowned for durability. They don't have the absolute best screens or the best specs for gaming. But they last and the T and P series are worth buying used from some company getting rid of their 5 year old models because they don't really die.

I'm currently on a ThinkPad right now as I type this. I would say overall they're fine. Lenovo tends to not fuck with them since they are the business model, and companies will drop them if they try any shit. I've also noticed that the laptop is pretty easy to repair, and sources spare parts for. I've replaced the screen on various models like 3 times, the keyboard once or twice, and the battery once. Really I just love the track point and it's hard to find laptops that have that feature. I've been running Linux on my current machine for years with no issues specific to my laptop.

I still use a T440p pretty regularly, but I also have a X1 Carbon Gen6 that I like as well. I had another one in between those two that was pretty nice, and I've also had the opportunity to use a few of the most recent X1 and E series laptops as well. They are nice and light compared to the older ones. Build quality overall seems reasonable for the price, especially when they're a few years old on eBay or similar.

I'm using a x1 carbon from 4 years ago and it's great, super happy with it and would buy another if I broke it. I ran mint on it for years and now cachy, it's solid

I have a pair of P53s that I love and hope last until the apocalypse. I have disassembled them a few times, spilled water on one (not too badly, but enough that I was worried about it). Added some Msata or M.2 SSDs to them (forget which). They're great machines. Not all Lenovo machines, and not even all Thinkpads are great, in my opinion, but generally if they've got the trackpoint mouse and aren't obscenely "slim" they'll probably be pretty solid reliable machines.