Nice to have some variety and choice, and this is certainly a very solid first version! Always room for improvement, of course. :)

• How to log in the first time is not at all obvious. If that empty circle was not in the corner where most Lemmy instances have a login link I would never have found it. At least this is only necessary to find once, but still, there's room to put "Login" text in that space.
• I like that the left sidebar with my subscribed communities is collapsible, but the community sidebar on the right is not collapsible. I think the latter is much less useful or commonly used for most users, so this is an odd choice IMO.
• Three vertical scrolling areas is not super great. I also get a horizontal scrollbar in the community list when collapsed. Why make the left and right panes "sticky" and scroll with the main column, then remain in place with further scrolling. If the right sidebar was collapsible, I don't see why scrolling with the main column would cause problems.