At least one invalid signature was encountered

There are a few reasons why you encounter these errors:

1. There might be an issue with the existing cache and/or disc space. In order to fix it you need to clear the APT cache by executing: sudo apt-get clean and sudo apt-get update.

2. The same goes with existing docker images. Execute: docker image prune -f and docker container prune -f in order to remove unused data and free disc space. Executing docker image prune -f will delete all the unused images. To delete some selective images of large size, run docker images and identify the images you want to remove, and then run docker rmi -f <IMAGE-ID1> <IMAGE-ID2> <IMAGE-ID3>.

3. If you don’t care about the security risks, you can try to run the apt-get command with the --allow-unauthenticated or --allow-insecure-repositories flag. According to the docs:

Ignore if packages can’t be authenticated and don’t prompt about it.
This can be useful while working with local repositories, but is a
huge security risk if data authenticity isn’t ensured in another way
by the user itself.

Please let me know if that helped.