I tried to do pretty much this on a Kobo reader and discovered the Kobo browser doesn't support javascript. :|
Like most DIY tinkerer solutions, unfortunately, which is why people like paying money for productised solutions - the time it takes to debug and troubleshoot home made solutions is often prohibitive for a lot of people who aren’t techheads.
"I had to reboot my raspberry pi"
"whoops rando eInk display doesn't do javascript"
... In short - if our parish priest above sees the original post, I'd suggest he give it a go. It's an hour to set up and won't cost him or his parish anything (aside from buying the eink display ofc).
If it turns out that the DIY solution is insufficient, or his parish is wealthy enough to spend money on a thing like this, great, then upgrade to that.