I'm not sure if you determined if all of this is a dvisvgm bug,
but if not:
Here is a MWE, which shows the issue. What happens is that
DVI creates corrupted DVI file or has an error making the dvi.
When dviluatex (or any engine) creates a corrupted DVI file (i.e.,
dvitype cannot successfully read it), under any reasonable
circumstances, it's certainly an error.
However, the LuaTeX developers fixed the previous DVI-generation bug,
and it could well be related. Unfortunately, we'd have to compile from
the original source to get the fix, and I don't see that happening.
I could report it to them to try, except:
Here is MWE
As discussed last time: to debug, the LuaTeX people need an invocation
of dvilua(la)tex, not an invocation of make4ht.
Best,
Karl
