@Nas and ujl bro, maybe u guys are maithil brahmins or upadhyaa bahuns of hills and so talk of upanishads and other orthodox brahmanical stuffs ,but thats not much part of nepali hinduism .our traditions are more shaiva and shakta traditions and not the later invented vaishnavism like in india.
our sanatana system of belief (at least for khas,magars,gurungs,kirati,tamang and newars) is the tantric pre-shankaracharya hinduism/sanatana system.so except the terai and pahad bahuns(though most of pahad bahuns are of khas ethnicity who converted post 10th century)we mainly have shiva and shakti worshipping traditions and tantric worshipping rituals. we have parallely our kul deutas,sime-bhume,banjhakri,bonpo gods ,kirati gods and other forms of anscestor worship.
also the temples in whole of nepal were worshipped with tantric rituals and most of them are worshipped so till date. our primary dietie have always been shiva in his primordial forms and the mother goddess in her shakti form since thousands of years.
only since the shah ascendence to power and the rana attempt to standardise hinduism to north indian hindu royals brought the rituals,books and traditions which we know today.
prior to that, people recited chandi and not geeta,machhindranath and gorakhnath were the royal dieties,animal sacrifice,weapons worship etc which is barred by vaishnavism was totally the norm of our culture.