I am absolutely NOT a developer, but I am trying to get this abandoned app to work

This is the code in a file called layout.erb which is HTML

```
<div class="container">
<%= yield %>
</div>

```

It's throwing this error:

SyntaxError - /wallop/app/views/layout.erb:53: Invalid yield:

I understand that they're using Bootstrap and that "yield" is a special term in Ruby and the %'s are supposed to print and evaluate the code -- I get all that, I just don't see why it's erroring.

This app was written a long time ago and abandoned, the devs moved on and made a commercial version of it, so they are not interested in helping update the old source, I am more or less interested in tinkering with it so that I can teach myself Docker and some other things.

I have not tried anything, just researched the error

I think this may have something to do with the fact that this is an old app and it was written in Ruby 2 and I'm running Ruby 3, but that is just a guess.

UPDATE:

This is exactly the same problem, the app is also using Sinatra / Thin:

<https://github.com/mocdaniel/dashing-icinga2/issues/121>

They fixed it by reverting to an older Ruby version, however I’m not sure I’ll be able to do that easily

I’m using alpine:latest and then running apk add ruby-json ruby-dev and ruby-bundler from the repo, it’s grabbing the latest versions…I don’t know alpine or Docker well enough to specify how to grab the older versions and I would prefer not to compile & install them manually.

It may actually be easier to just fix the code to work with Ruby 3.