KJ,
I'm in the planning phase for doing the Loop starting in 2021. I've been on most of the waterways of the Loop at one point or another, but doing the whole thing start to finish seems like a nice adventure.
I recently joined the AGLCA (greatloop.org) and it's probably worth joining when you're getting ready to go, but at $85/year I'd hold off while you're still in the "maybe someday" phase.
You probably would enjoy the book
The Looper's Companion Guide, which I also just recently got and strongly recommend.
For dreamers, Capt John's site (that Chaz linked to, above) is probably the best free resource. And each region has its own web sites, like the NY State
Canal system or the Trent-Severn. You could spend years Googling and reading up on each leg of the trip.
For all the talk (and all the blogs!) about the Loop, it's really a fairly small number of boaters, probably 200-300, who actually go every year. And only some of those finish.
The Loop is well within the abilities of an experienced river boater, since there is very little "real"
navigation involved, and you can do the whole thing without ever leaving sight of land.
I too have looked for a more active Loopers forum. Probably the AGLCA site is the most active, but even that doesn't really have a huge volume. Reddit has even less. The AGLCA experience is more personal, since it's only paid members.
Posting there is as likely to get you a direct e-mail response (since e-mail addresses and names are listed) as a posted reply.