PolyMC recently (17/10/2022) went up in flames. The lead maintainer, LennyMCLennington started being transphobic, removed maintainers from the GitHub org/repo and the Discord.
The commit that started this entire thing: https://github.com/PolyMC/PolyMC/commit/ccf282593dcdbe189c99b81b8bc90cb203aed3ee
UPDATE (18/10/2022): Further theories on what is going on with PolyMC: Imgur
In PolyMC settings, go to API page and paste this link under Metadata Server: https://meta.prismlauncher.org/v1/
And also change your Microsoft API key to: c36a9fb6-4f2a-41ff-90bd-ae7cc92031eb
This will make auto updating of PolyMC meta files use PrismLauncher's files, so your computer can't be compromised by possible malware added to PolyMC's meta server after the takeover.
https://github.com/PlaceholderMC/PrismLauncher
Download the latest release