Converting GW-BASIC to the Z80

It seems potentially a "call for help":

"I appreciate help if this is the kind of rabbit hole you'd like to burrow in."

The current status is of the conversion:

"a lot of instructions being generated are invalid and the code generator has to be reviewed."

If it is, and the author is reading this, I suggest documenting exactly one by one the open issues. There are surely readers here that are able to "see" and propose a fix for some details without investing a lot of energy upfront to first figure out what the issues are.

Looks like others have tried an x86 to z80 asm converter before. Maybe some ideas there:

https://github.com/Zany80/x86-to-z80

BASIC on the Apple ][ did a linear search from the start of the program for each GOTO and GOSUB. I wonder if GW still does that...