I maintain a similar index-of-indexes but it's intentionally non-curated, restricted to indexes that use the OPML format, and uses autodiscovery to expand the list. The site needs some work, but it's up to 356 indexes.
I'd recommend looking at anything with "planet" in the name, there are a bunch of tech communities that manage community feeds and they are high quality. There are also a ton of personal blogroll recommendations via micro.blog too.
I also have a separate list of my favorite parts of the internet I plan to eventually turn into something like this: https://wilderness.land/ (my inspo)
https://blogroll-network.alexsci.com/blogrolls/
I'd recommend looking at anything with "planet" in the name, there are a bunch of tech communities that manage community feeds and they are high quality. There are also a ton of personal blogroll recommendations via micro.blog too.