Replacing the crappy panels that come with the T480 with a better 4K panel is a somewhat popular mod, and it seems that most people opted for the BOE NV140QUM-N53 as the replacement panel.
However it is not the best 4K 14" 16:9 panel, I think that would be the AUO B140ZAN01.2, as according to panelook.com it has better brightness and color gamut while having only slightly worse contrast.
The B140ZAN01.2 is a 10 bit (8bit + frc) panel and i was a bit concerned that it would not work as as far as i know no one had put a 10bit panel in a T480 before.
I had ordered a B140ZAN01.2 from aliexpress a few weeks ago and it arrived today. I have not yet fully installed it but i tested outside the laptop, and i can confirm it works, and despite being extremely bright at 600cd/m² it did not blow the backlight fuse even at full brightness.
I will post an update on the full replacement process when i get around to it.
update:
I have got the new panel installed, The installation process was nearly the same as detailed in this reddit post: https://www.reddit.com/r/thinkpad/comments/jde1a9/the_hackinpad_t481_heavily_modded_t480/
The panel used in the post is a different (worse) version of the one i used and has identical dimensions.
The end result is good and i dont think anyone could tell the panel has been swapped by just looking at it. The only issue is that the panel is offset up by about 1mm, this is due to the pcb at the bottom being taller, i could open it up and remove more of the raised plastic bits on the inside of the lid to get the panel better aligned but the slight misalignment is not that noticeable so i will just leave it be.
The panel itself is quite comparable to the 2560x1440 hdr 500nit panel (AUO B140QAN02.0) in the x1 carbon gen 6, the biggest difference is that the B140ZAN01.2 gets even brighter, color performance and black levels looked very similar.
If you have any questions or would like to know how to do this mod yourself feel free to ask, i left out a lot of details that have already been mentioned in the other T480 4K mod posts.
updated link with more pictures: https://imgur.com/gallery/s9nblnD
How do you find compatible panels? I've got a Stone laptop that's ideal for me in every other way, but it's got a 1366 x 768 panel, and the resolution is just too low.
You need to find out what exact panel you currently have, you can try googling and i think hwinfo64 shows exact panel model. Then you should look for what dimensions and connector your panel has, you can find this info on panelook.com. laptops made in the last 10 years mostly used edp connectors, there are a few different ones that are not compatible with eachother.
Panels with resolution that is 1920x1080 or lower use a 30 pin connector, Touch panels use a 40pin connector. Higher resolution panels (2560x1440, 4K) also use a 40pin that looks the same but is NOT compatible with the touch 40pin. Newer laptops and panels sometimes have a connector with 0.4mm pin pitch which is not compatible with the normal 0.5mm pitch connectors.
If your laptop was sold with a high res panel option you can find a 40pin cable for it, But as the motherboard side of the cable is non standard if your laptop only came with lower res panel options you will have to stick to 1920x1080 panels that have the 30pin connector.
Look for panels on panelook that have a compatible connector and have the same or a bit smaller outline dimensions than your current panel. Once you find a good panel you can look for it on ebay and aliexpress, You should message the seller to make sure that you are getting the exact panel as often they will send whatever compatible panel they have in stock that can be a lot worse.
The panel you get may just be a drop in replacement or you may need to modify the lid as even if the outline dimensions are smaller the pcb at the bottom may be wider or the connector in a sligthly different place.
There are still a few possible issues that you can run in to, Some laptops have a panel whitelist or are designed in a way that makes panel swaps hard or impossible, you should try to find out if anyone has done a panel swap to your laptop before.
That's some great advice, thank you :)
I'm pretty sure that it had at least a 1080 screen option, but it's a generic laptop that was sold under two or three brands that I've found, and one of the brands had a few very similar models e.g. the P11b and P11c.
I'll do some digging tomorrow and start the search. Thanks again for your help :)