When I started I clicked on the top right button, chose Normal Mode, and pressed Next. The game looked like it had locked up. I was pulling up the console to look for errors when it finally loaded. I would suggest adding a loading screen to give the player feedback that something is happening.
I then got a message about completing 10% and a reward. After that I was taken to a pause like screen, and got the browser prompt for a username.
When adding things like leaderboards, it is a good idea to make them optional. Not everyone wants their score/progress publicly shown. Having a popup right as you start requiring you enter a username that cannot be changed is a potential way to lose people. Even if some may be willing to submit a final score, if they have not played and don't know if they will like the game, or how well they will do, they may be less likely to enter a name. Even if they do enter something, you are more likely to get generic names that people will use when unwilling to commit to putting their gaming name into it. Being unable to change it if they decide they do like the game, will annoy some people.
As someone who plays jam games, and especially as a jam host, I am always aware of and concerned about security. Having a game I don't know actively sending unknown data to a remote server is a serious concern these days. With this game using JS, I stopped playing and started looking at the code to see what it was sending and where. SimpleBoards seems to be a legit site and the current data sent seems fine. Still, not everyone will do that, and some may decide a game that is sending random data is not worth playing, so offering an option to disable it will help to not lose a set of players. The option to disable needs to be available before prompting for a username, or available from that prompt.
After the popup asking for a name, I was unable to proceed. I clicked on the Back button, but nothing seems to happen. I tried again and checked the consol for errors. I saw the score was regularly being saved, but that was all it was showing. I also noticed that the music sounded like there were multiple instances playing, so I think the button is loading the game, but not hiding the menu screen, and keeps loading/starting things.
I refreshed my browser. When I went to the settings from the main menu it worked fine to get back to the menu. I then pressed play and it loaded the game. I was still seeing regular console messages about score submissions.
Since you have made updates to the game, it is possible there are bugs for those who have played older versions and have the old save file/progress being loaded. When making breaking changes you need to either have the loader include logic to update/convert the old save file, or start fresh, with a message to the player about it.
As someone who only plays this once a month, among many other jam games, coming back to it and continuing in the middle, I don't remember all of the controls. I recall they weren't all that clear to start with. I would highly recommend adding a way to see all of the controls for the game while playing. That could be as simple as putting them on the game page. Adding a way to see them from the pause screen would also be an option.
I paused to check if they were there, going to the options screen, and then ran into the same issue from earlier of not being able to use the Back button to return to the game. From the initial pause screen the resume button did work.
When I got into the game it looked like I was continuing from my old game. I was not at the start area, but it also looked like all of the keys and coins had respawned.
By the time I was in game and looked at my stats, I had over 45,000 coins. I don't recall getting that many the last time. I think it may have something to do with the other bugs. As I was writing this out I saw another batch of console messages about submitting score to the database, and my coins went up by 1,000. This seems to happen every few minutes.
The new gold merchant using in-game currency is much better, and adds more to seek out.
The grey merchant that sells blocks give the message about needing a block and placing it next to them, which seems odd.
I placed a block on one of the people asking for a block, instead of next to them. I could then no longer interact with them.
Not a big deal, but in an area with 2 people asking for blocks, I did both, and after the message of the second one completed, before it faded out, the first person showed back up briefly.
It would be nice if placing blocks was done in the direction your character was facing/had just moved. Having them appear behind you can be very problematic. From what I can tell it always appears to the right side of your character.
Your supporter pack shows up in the regular coin based shop, but does not have a price showing. The devlog said it was 999 coins.
I decided to use my large supply of coins to do some testing and buy up blocks. I bought a few things, including some of the new token coins, and was at one point taken to the broken pause screen. Upon refreshing the browser and restarting, all the coins and keys were back in the world to be collected. I still had my score and collected items, just that I could not go through and collect things again as well. The 1,000 coins I get every few minutes does not alter the % complete, but recollecting things on the map does. I intentionally went to the options screen and pressed the Back button, then restarted the game, and again the collectables respawned.
While testing I got the 30% completion message, so was able to see what should have shown for the 10% message, but was hidden by the options. This brings up another thing to keep in mind. If someone should get a reward at a certain point, but the game crashed or otherwise prevents them from getting it, you should track if they got it, and make sure they are given a chance to still collect it when they restart.
At this point I figured some of the bugs may be from the old data, so I decided to Reset. After pressing Reset several times I pressed Back and was taken to the menu.
After typing here I find I need to click into the game window a couple times to get it to accept inputs again. I started a new game and things looked like it had restarted. I double clicked and got the options menu. Back took me to the menu screen. I reset again, refreshed, and tried again. When starting, with the initial message showing, if I click on the game it takes me to the menu. From some more testing, it looks like it might be time sensitive. If you click too soon after loading into the game world it seems to happen. The message had already started showing when I clicked, so it wasn't like this was a really quick thing. Retrying and waiting a few seconds after the message finished before clicking and things worked fine, at least on the last time I tried it.
At this point I could spend a bit of time restarting with the bug and get 100% completion, just from that first area. Just letting the game sit while I do something else I can come back and buy anything I want from the shops. After restarting I left the game up while I finished writing my feedback. As I am finishing up I have over 18,000 coins accumulated, and I am still standing on the starting tile.
As to your question about paying for a "DLC", no, I would not pay for this game or any expanded content for it. This game is still very buggy. The game is growing, and many things are improving, but it is not ready for a paid release. You should get all of the features in, then polish and bug fix them, before starting on paid content. With this release it feels like you threw in a bunch of changes without enough testing. It is important to keep in mind that if you want to sell a game, then stability and being as bug free as possible is important. We indie devs cannot get away with massively buggy releases the way AAA studios can. One of the kids pulled this up to play, got the initial bug preventing them from playing, and decided to move on to something else. Something to keep in mind is that while adding more features can build out a game and make it feel better and more complete, it also adds more code to debug. As a game grows in complexity it gets harder to debug, even with good clean code. If you rush to add new features without good planning and implementation, you are going to create more problems for yourself in the future. Take the time to do it right, and test your changes before releasing an update, especially if you are trying to get people to spend money. I really want to emphasize this point. There are plenty of indie devs putting up simple random projects for fun with varying levels of quality, but not charging for them. You are very focused on making money on everything you release, and that means you need to meet a much higher standard than free stuff. Your current releases are not up to that level.