I’ll just say absolutely NO to making new players take tests and tsumego and stuff. Most would just close the browser and never come back, which would be the normal reaction.
Imagine going to a new dance club (as a trophy winning dancer or someone who just wanted to check out that place faint music is coming from) and being stopped at the door for “just 5 minutes” for someone to ask you how many feet positions you know, if you’ve danced before, what style of dances etc.
Just getting a dancing partner for starters is the goal.
And FYI being stepped on is much more painful than a bag of sand or air online.
Most solutions suggested are all for rank accuracy, seasoned players looking back, but I see once again the distinct lack of empathy for clueless newbies. inb4 I expect experienced players who hop online to be more understanding of having to play a few games to adjust, after all they surely know how ranks work.
What about a simple introductory window of “to quickly assess your rank, we start you at about 15kyu. It will take about 10 ranked games for the system to assess your actual rank. Feel free to challenge bots or other players. You can also play unranked games! Welcome.”