How to apply a patch - Community Edition - The missing manual?

[MudGreg]

I followed the instructions to the letter but hit several issues (one was my fault so writing as a tip for everyone, rtm):

1. After the update all my configuration changes had gone - This was my fault as I should have put them in the .env.local file as per the instructions. Restored a backup and that was all good.
2. When I ran 'yarn run webpack' I got the error "Module not found: Error: Can't resolve 'akeneo-design-system'". The answer to that question is here: Module not found: Error: Can't resolve 'akeneo-design-system'  pim-community-dev#15016
3. Everything installed, up-to-date, restarted but getting a 500 error. Arggghhh.... This is cache related. We run ours through Bitnami and I have found that the php-cli commands run as a different owner to the web app so the cache is created in an unusable state, you need to check both the owner:group and the read-write permissions in the /var folder
4. Finally got it to appear but then just got the loading graphic and nothing else. Web debugger revealed that the javascript bundle wasn't loading still. To fix that I ran the commands in this order (thanks to a hint in a WebKul support document):

• yarn run webpack
• yarn run update-extensions
• yarn run less

I am hoping that helps others that might hit this problem and save them time in debugging the issues. And I'm certain this doesn't affect everyone, but I figured writing it down would potentially help some people.