MacBook Pro - doesn't boot - magsafe stays amber without battery

Hello, I have an issue with my mid-2014 13” Macbook Pro (A1502)

On Tuesday, I reached my computer after it was left charging for a while, opened it, woke up with fans spinning at full throttle, nothing on the screen, and after 30 seconds or so, it shut down by itself. Tried to restart it a number of times, with various results ranging from “no life at all” to “fan at full speed, apple logo on the screen, booting up for 15 secs and then shut down”. Tried SMC reset, successful (magsafe turning green then amber), but no change. Impossible to do a NVRAM reset, boot into recovery mode or diagnostics mode as the mac would just shut down before booting macOS.

Yesterday, it just didn’t want to start anymore… no sign of life except for a little noise in the case when i powered it on (it was the fan - see next paragraph).

Tried charging it, Magsafe turned amber, little heat coming from the case, but it stayed in that state for hours, longer than it usually takes for a full charge (even though it was probably at approx. 90% charge at least when I plugged it in). First weird issue.

Today, I decided to have a look inside, took out the motherboard, didn’t see any kind of visible damage. No water, nothing except a certain amount of dust.

Cleaned it up. Tried to boot. The computer actually reacts to the “power” key on the keyboard (so that’s not the issue). What actually happens is that the fan spins at slow speed (close to being silent), but that’s it. Tried booting with the battery disconnected, no change BUT I noted the MagSafe port turned amber… seems weird if there’s no battery to charge.

From my research and gut feeling, I would guess a shortage in the motherboard, but I do not have the knowledge and tools to diagnose further if that’s it. And it’s a 2014 MBP in a not-so-great shape (right speaker needs a replacement, screen is worn out…), so I’d rather upgrade for a new computer than spend hundreds on getting it fixed. Is there anything else I can try that’s reasonably cheap?

Thanks in advance ;-)

L.