Thanks for the feedback! this is useful for me.
"The onboarding steps are confusing." Anything in particular?
"Login page could use css ;)" I'm not very good at frontend development, so most of the frontend stuff is just what I could hack together. If you have frontend skills, you are welcome to open PR's :)
"When I open squeaknode it lands on Timeline page. It's not clear what to do next." When the timeline is empty, there should be a welcome message that gives some basic instructions (follow people/create posts). Were you able to see the welcome message?
"I click on the pen button (the FAB action button with primary color means "the most important next action"), but in the dialog I don't have a profile, so I have to close it again." I should probably have a button directly in the dialog to navigate to the "Profiles" page, to make this easier.
"When I post first squeak it says "9 minutes ago" even though I just literally posted it." This happens because the timestamp inside the squeak is based on the most recent bitcoin block hash. That's how I am able to share timestamps trustlessly between peers.
"When I try replying to the squeak - my profile should be selected by default (also profile should just be selected globally, I don't want to toggle it in every. dialog)" I am working on this... it is currently an open issue: https://github.com/yzernik/squeaknode/issues/1146
"The CSS could use some help - fonts are too big in replies, missing paddings, random box shadows, too many colors, unclear next action." Yeah, I know :) it needs a lot of work
"Buttons are missing titles, so it's not clear what it does. When I click on resqueak button on my own post, it looks enabled, but then does nothing." There should be an alert message that says "Unimplemented" when you click. Can you make sure that you are running on the latest Umbrel release?
"It's not clear how to find anyone else. It would be great if you have some nice account to follow by default, e.g. yours. That would help a lot if I want to actually try some interactions early on." That's an idea that I am considering.