Let’s encrypt, and any other ACME based certificate of authorities will let anyone without identity verification create a SSL cert that will work in any browser. This creates trust issues with certain clients browsing web. For example my work (50k+ employees) uses Zscaler to evaluate if a website is safe and it 100% will down-votes any site that uses let’s encrypt due to the lack of transparency. Zscaler will eventually block that website from employees if the score falls too low. Having an SSL cert that you pay for gives cyber security, firms - rightly or wrongly - an additional level of confidence that your identity has been verified.

Full disclosure: I use let’s encrypt on all my self hosted docker instances via Coolify which suits my needs. If I were to set up an ecommerce or other site that needs to guarantee trust, I would absolutely use a paid ssl cert.

The easiest way to run local LLMs on older hardware is Llamafile https://github.com/Mozilla-Ocho/llamafile

For non-nvidia GPUs, webgpu is the way to go https://github.com/abi/secret-llama

Without knowing anything about your specific setup I’d guess the issue is with docker not playing nice with your OS or vice versa. Can you execute the standard docker hello-world app? https://docker-handbook.farhan.dev/en/hello-world-in-docker/
If not then my money’s on this being an issue the OS. How did you install docker on mint, using sudo with a package install?
Fyi don’t feel bad - I installed docker on 3 different Linux distros last month and each had their quirks that I had to work my way through. Docker virtualization is some crafty kernel-level magic which can go wrong very fast if the environment is not just right.