Fossify Gallery on the official F-Droid repo
The removal isn’t directly related to the buyout/fork. Simple Gallery was taken off of F-Droid due to a dependency on the nonfree Google VR being discovered by IzzySoft¹ ². Fossify’s fork has removed the dependent features to be compliant³.
Not getting updates doesn’t make any app inherently bad. Possible bugs just won’t get fixed. If an app is feature complete and everything works as they should there’s no need to update it.