It seems to me, that I'll try with Kext on my MacBook Pro 15'' 2014 too... Here's my tortures during last few days...
Full description on Reddit
Now about 5 hours on Catalina that I installed at separate Volume of SSD as addition to Mavericks (first OS on this Mac) and no problems...
Glad you found somethhing that works. Your story mirrors many others on this forum. My MacBook Pro Retina from mid 2014 started running into similar problems about two years ago. Apple replaced the battery with a new one which did not help. I also had my Mac's logic board replaced earlier (before these issues started).
Others here also report replacing or upgrading SSD helps. The two workarounds that have appeard to help the most is removing the Thunderbolt NIC kext (actually deleting the kext file) or keeping the CPU busy in an endless busy-wait loop running as a simple Python program or even a bash script.
This weekend, I'm upgrading the SSD and will report back if it helped or if I go back to removing Thunderbold drivers again.