All classes, gain a feat every other level.
2,4,6,8,10,12,14,16,18, or 20
On levels 4, 8, 12, and 16 when you gain an ability boost (2 ability points), you do not gain a feat. Instead you may choose a feat instead of an ability point. So you can get 2 ability points, or 2 feats, or 1 feat and one ability point.
Feats are as they existed in 3.5 and will be ruled individually when or if they are found to not mesh with the campaign.
To be clear that is all class’s, not to be confused with bonus feats earned by specific class features, I assume.