MountCam

Mounting a vehicle or rideable mob moves the camera behind the player, and getting off restores the first-person view. The author notes say the switch also happens when a player gets on a vehicle, and that the switch on dismount is quick. Vehicles themselves are not affected, and the author notes that the mod does not work with vehicles in one place, so its effect should be checked on the vehicle type in use. It works with rideable mobs. The mod is client-side only, so only the client needs it, and it is published for Fabric across 14 release versions, 1.21.1 – 26.1.2, under All rights reserved.

Installing Cloth Config API and Mod Menu is optional, and both can be used to change the mod's settings. Customization of mount support is only available on 26.1 and later.