In addition, I am not sure what your purpose of exporting html is. If it is to be published online as a static file, it may be better to export markdown and then be processed by a third-party framework?
My main purpose is to archive notebooks. I found that html with folders provides the best readable version for screenshots, mermaid and KaTex. There was something else not perferct with the md expert, but I need to check. Generally spoken I would perfere md over html if this would work..
If it's just a backup, I recommend using jex export, it's actually a tarball, you can view it with a decompression tool, plus it's a full backup compared to other solutions, there's a joplin plugin to run it automatically.
It might not be that readable, but for backup purposes it's the best.