The best model I've seen for a digital community structure is Mighty Network.com. I have been in several very vibrant (and financially successful) communities using this platform, and I think this is worth the dev. looking at as a model.
They have integrated everything discussed in other posts on this topic + several different payment gateway options, which are customizable to each membership community's needs. There are endless ways to use a 'might community', from selling online services to having a fully engaged community that offers live training, course upsells, private networking areas (behind payment gateways), PLUS a discord-style live chat feature.
As a user, this live chat function separates the static communities from those that are 'living.' This allows the owner/mods to see how engaged their members are in live time. It offers the ability for sub-communities (behind paywalls) as well as 24-7 user engagement. The company Might Network is all about community, just like HL, so I think it would be a great model to follow.
The flexibility and freedom that each community owner gets to customize their community (both in branding and features on the paid plans) allow each community to have a unique feel, even if everyone is on the same operating system, just like HL.
It's a wonderful model because, like HL, you only pay for what you need. It is so seamless that it allows those who need static features to have them, but for coaches and consultants who are in the business of community creation, it gives that 'in person' feeling, even if it's focused on virtual events. Anyway, I wanted to throw that out there since I keep hearing about skool (I had not heard of this software before Dallas).
[This was posted as a response, but I felt that i should be it's own request after posting it]