What do I need to do to hook up ActionCable on nginx and puma?

I'm having trouble getting ActionCable hooked up in my prod environment, and related questions haven't had a working solution. I'm using an nginx+puma setup with Rails 6.1.3.2 on Ubuntu 20.04. I have confirmed that redis-server is running on port 6379, and that Rails is running as production.

Here's what I'm getting in my logs:

I, [2021-05-25T22:47:25.335711 #72559]  INFO -- : [5d1a85f7-0102-4d25-bd4e-d81355b846ee] Started GET "/cable" for 74.111.15.223 at 2021-05-25 22:47:25 +0000I, [2021-05-25T22:47:25.336283 #72559]  INFO -- : [5d1a85f7-0102-4d25-bd4e-d81355b846ee] Started GET "/cable/"[non-WebSocket] for 74.111.15.223 at 2021-05-25 22:47:25 +0000E, [2021-05-25T22:47:25.336344 #72559] ERROR -- : [5d1a85f7-0102-4d25-bd4e-d81355b846ee] Failed to upgrade to WebSocket (REQUEST_METHOD: GET, HTTP_CONNECTION: close, HTTP_UPGRADE: )I, [2021-05-25T22:47:25.336377 #72559]  INFO -- : [5d1a85f7-0102-4d25-bd4e-d81355b846ee] Finished "/cable/"[non-WebSocket] for 74.111.15.223 at 2021-05-25 22:47:25 +0000

This happens every few seconds. You can see matching output in the browser console:

For one, I'm pretty sure that I need to add some sections to my nginx site config, such as a /cable section, but I haven't figured out the correct settings. Here's my current config:

server {    root /home/rails/myapp/current/public;    server_name myapp.com;    index index.htm index.html;        location ~ /.well-known {                allow all;        }        location / {        proxy_pass http://localhost:3000;        proxy_set_header Host $host;        proxy_set_header X-Real-IP $remote_addr;        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;        proxy_set_header X-Forwarded-Proto $scheme;    }    # needed to allow serving of assets and other public files    location ~ ^/(assets|packs|graphs)/ {        gzip_static on;        expires 1y;        add_header Cache-Control public;        add_header Last-Modified "";        add_header ETag "";    }    listen 443 ssl; # managed by Certbot    ssl_certificate /etc/letsencrypt/live/myapp.com/fullchain.pem; # managed by Certbot    ssl_certificate_key /etc/letsencrypt/live/myapp.com/privkey.pem; # managed by Certbot    include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot}server {    if ($host = myapp.com) {        return 301 https://$host$request_uri;    } # managed by Certbot    listen   80;    server_name myapp.com;    return 404; # managed by Certbot}

Here's my config/cable.yml:

development:  adapter: asynctest:  adapter: testproduction:  adapter: redis  url: <%= ENV.fetch("REDIS_URL") { "redis://localhost:6379/1" } %>  channel_prefix: myapp_production

In config/environments/production.rb, I've left these lines commented out:

  # Mount Action Cable outside main process or domain.  # config.action_cable.mount_path = nil  # config.action_cable.url = 'wss://example.com/cable'  # config.action_cable.allowed_request_origins = [ 'http://example.com', /http:\/\/example.*/ ]

I have not mounted ActionCable manually in my routes or anything. This is as standard of a setup as you can get. I'm thinking the answer lies centrally in a correct nginx configuration, but I don't know what it should be. Perhaps there are Rails config settings that are needed too, though. I don't remember having to change any when deploying with passenger, but maybe puma is a different story.

Update

I also noticed that a lot of the proposed solutions in other questions, like this one, seem to reference a .sock file in tmp/sockets/. My sockets/ directory is empty, though. Web server's running fine besides ActionCable though.

Update #2

I also noticed that changing the config.action_cable.url to something like ws://myapp.com instead of wss://myapp.com has no effect even after restarting Rails. The browser console errors still say its trying to connect to wss://myapp.com. Possibly due to how I'm set up to force redirect HTTP to HTTPS. I wonder if that has anything to do with it?