I have also been having very similar problems with the same error messages. Using Emacs 26.2 on GNU Linux (Ubuntu 19.04). Attempting to install the delight package. Exact same error with emacs -Q. Same configuration is working fine under macOS, so seems to be GNU Linux specific. Changing to use HTTP instead of HTTPS fixes the problem. Note however that HTTPS to the melpa repository works fine. Note also that this setup has been working fine for ages. Last fresh install was only a couple of weeks back.
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