Awesome! I've been using Beancount/Fava for over 2 years now and this looks really slick.
One thing off the bat I noticed, it doesn't look like custom Tags are supported? I use tags all the time in beancount, say to filter for a trip #trip-europe-2022 which would break down my cash flow and balances (and the rest of the fava UI) for a subset of transactions.