As reported against the Provider plugin, since an upgrade in December, all providers started showing as unknown.
Today we disabled QueuedTracking and provider names started being re-populated again from the geoip database. On re-enabling QT, providers went back to being stored as unknown.
Would be nice to get this fixed and we've been able to replicate on a new install on a new server from latest stable version.
Ref: matomo-org/plugin-Provider#10