My case maybe a bit different from u, u can download the UMA script from
https://opsive.com/downloads/?pid=923. There are 3 files i use, UMACharacterBuilder, UmaAbilityBuilder and UMA ItemPickup. i just copy the onCharacterCreated method from UMACharacterBuilder to my avatar loader script. then i remove all related to UMA. Mainly replace "umadata" to my own gameobject, for ur case maybe Transform i.e. onCharacterCreated(Transform data). then replace the umadata from UmaAbilityBuilder and UmaItempickup to Transform as well.
if u run the method onCharacterCreated with ur new character, it will add all the component on ur new character and setup ur rigging with items on right and left hand and other neccessary.
thanks, i will try again to replace all the component with new avatar and see if it work with pun2.
if u still cannot get it work on UMA script, i will paste my code here.
lastly, if u r not importing new avatar on runtime, can take a look at photon ownershiptransfer when u spawn new player from ur resource folder.