The key listed on the instruction page
https://software.intel.com/en-us/articles/installing-intel-free-libs-and...
specifically, this file:
wget https://apt.repos.intel.com/intel-gpg-keys/GPG-PUB-KEY-INTEL-SW-PRODUCTS...
is old, and has just expired. There will be a million failures; do not panic; I hope Intel will fix that very quickly.
# curl -Ss https://apt.repos.intel.com/intel-gpg-keys/GPG-PUB-KEY-INTEL-SW-PRODUCTS-2019.PUB | gpg -
gpg: WARNING: no command supplied. Trying to guess what you mean ...
pub rsa2048 2016-09-28 [SC] [expired: 2019-09-27] <<<=== THIS
BF4385F91CA5FC005AB39E1C1A8497B11911E097
uid "CN = Intel(R) Software Development Products", O=Intel Corporation