The opinion seems to be that they are self funded through the opium trade.
https://nazuksuratehaal.com/who-funds-taliban-in-afghanistan/
So looking into the opium trade. There is this graph. Showing that the drugs the middle east, china, africa, and south America produce are all flowing into Europe and North America. They wouldn’t be selling drugs there if there wasn’t money to be made.
But there is still a question. The US funded the Taliban back in the 1980s to support the Taliban’s effort to push out the Russians.
https://www.lewrockwell.com/2019/02/no_author/30-years-after-soviet-afghan-pull-out-cia-funded-mujahideen-war-backfired-on-us/
So is China or Russia, or both funding the Taliban now to push out the US?
https://www.rand.org/blog/2021/07/china-and-the-taliban-begin-their-romance.html