I finally got around to resolving a Slack "GPG check FAILED" error that occurred during package updating using a resolution for Linux (beta) provided by Slack.
$ sudo dnf update -y
bash output:
GPG key at https://slack.com/gpg/slack_pubkey_20210901.gpg (0xF6C6FFD4) is already installed
The GPG keys listed for the "Slack" repository are already installed but they are not correct for this package.
Check that the correct key URLs are configured for this repository.. Failing package is: slack-4.28.171-0.1.el8.x86_64
GPG Keys are configured as: https://slack.com/gpg/slack_pubkey_20210901.gpg
The downloaded packages were saved in cache until the next successful transaction.
You can remove cached packages by executing 'dnf clean packages'.
Error: GPG check FAILED
Back in November 2021, there had been conversation on Reddit, where folks came to conclusion that Slack ceases support of Fedora with small note on their support page that
Starting March 1, 2022, Slack will no longer support Fedora Linux distributions.
So effectively what you see is withdrawn support from Slack - no more new packages.
They don't say but imply that your choice is: