Sorry to hijack this thread. I'm using a Dec Vt220, 420 and 510. You posted a git link back in 2020 with your improvements to making it useful. The link no longer works. Are you able to provide an updated link?
I have a site named yin at neocities, from the index page, bottom-most link. I'm not linking directly because it redirects to weeb trash if there is a social site in the referrer.
Also if you have questions about the VT520, you could join ##asm on libera IRC.
Also if you have questions about the VT520, you could join ##asm on libera IRC.