Update: at end of the day I disconnected the ethernet cable from the ethernet adapter, leaving just the pity adapter attached to my thunderbolt port (since I have two TB-ports: I use the port next to the power connector). Also, I disconnected the power cord. Unless reporting otherwise in the next few days, this may be enough for you too. @ddownn Thanks for the tip! Guessing you mean a 'dummy display emulator': it is €8,- in the Netherlands and they come in al sorts of colours, even gold finish, which is great! ;-)

Same problem here: Using a MBP retina late 2013, 16Gb/512Gb/2.3Ghz Quad core i7. screen turns black, with backlight still on, fans start to spin, system crashes note: after startup, some interesting processes appear, like MRT, using al lot of CPU power for a short wile. Apple's standard procedure after something indefinite happened? Suspicious actions (some time) before the problem appeared: using a corroded power-connector (just replaced) upgrade to Big Sur putting in a new battery using a 45W power adapter. (in this order) Attaching ethernet via thunderbolt + power adapter works for me. Not tested without power adapter yet. No further actions like python script etc. Next step is to connect something useful via thunderbolt, like a portable hdd (and attach it to the lid with velcro tape, like my phone). Luckily, I have a macbook air 13" mid 2011 that is still running without problems! k.r. Olav