Is there an M68K CPU that’s considered “fast enough” for most things today or is this a fun retro-computing effort?

There actually exists an insane project by some madmen that implements a modern OoO 68k-compatible core. It has a typical IPC north of 3! (compared to a real 68k, which is lucky to have an IPC of 0.3 on a good day). It is truly a work of marvel!

http://www.apollo-core.com/index.htm?page=features

afaics this is used in Amiga accelerator cards and doubles the performance of an Amiga A4000 which ran at 25MHz. So nothing we'd really consider modern.

I suspect you might be mistaken. The IPC uplift at same clock rate compared to a stock 68k is over 5x in all cases, often more.

this is a proprietary FPGA design. The effective performance is limited by FPGA technology for now. Maybe additionnal design work would be required for an ASIC targeting latest foundry nodes.

As well as the Apollo FPGA emulated one there's an ARM based M68K emulator https://github.com/michalsc/Emu68

I don't know if the NXP ColdFire CPUs are available anymore, but they continued development for a while.

https://en.m.wikipedia.org/wiki/NXP_ColdFire

I keep getting LLVM confused with LLM. So I assumed this was a LLM fine-tuned for writing M68k assembly code somehow.

Not sure about M68k but maybe there is an 8 bit system with enough documented assembly code and combining that with the text of the manuals.. maybe there is a way to somehow make a text-to-8bit assembly program AI model.