Can you check the console and see if there are any errors?
To check for errors, first open the developer tools by pressing Ctrl-Shift-I on Windows/Linux or Cmd-Opt-I on macOS, and then go to the “Console” tab. If you want to save the error to a log file, you can right click on the error and choose “Save as…”.
I notice that there’s a wrong hotkey guide about opening the developer tools in the help doc, it may let some people who is not familiar with Electron feel confused. I’ll fix it up, and make a pull request on the docs GitHub repository.
If you are building or modifying your own css, you can open the developer tools by using Ctrl/Cmd+Shift+I to get information on the elements you want to customize.
Edit: Looking a little closer at the mimeapps.list because of URL Scheme doesn't work on Linux, it turns out that opening Obsidian makes it the default application for html files, instead of the browser. I don’t know if this is related, but this is definitely a bug. I don’t think Obsidian is intended to open other local html files, but even if it is it should be added to the [Added Associations] section instead of making it the default.
LOL, yeah, as soon as I’d finished posting and hit the Back button (well actually, I use Alt-Left Arrow) to get back to the search listing, I noticed the “Resolved help” tag just below the thread title (I hadn’t noticed Licat’s post somehow though).
I’m figuring out this particular BBS forum bit by bit, I haven’t been doing forums in quite a while, and this one seems to be fairly different from others.