wife has a T440 and TRUST ME 4 GB is barely enough to power Win10.
I have run Budgie with 4GB just fine but youtube only, no gaming, and no real streaming. That would probably go for Mate as well.
Want to get the wife 8GB for that slot but that kind of research sucks--maybe after a tall boy later...LOTS OF T4XX submodels under the 420 430 440 etc that your head might spin. Ex: maybe 5-6 configurations of 440--different in specs--and very hard to tell there's a top secret Lenovo sheet I used to have somewhere in pdf form about identifying the variations and variations...maybe 3 tall boys. Don't judge😉
I bought her a dock as well. Loves the bigger screen. Docks have limitations but you will get used to it.
WORSE...I did some research and found out many of the T4XX series have a single slot for memory and many have two slots for memory. So for some models you can buy another 4 and for some models you only have a single slot so you have to buy an 8. How to tell? Beats me!!!🙁. Tall boy research for sure.
PITA but I like Lenovos.
(PS--whatever became of the 250LB server you inherited?) edit/sp