In the Mahayana traditions it has the traditional beliefs of Dharmapala, i.e. a dharma protector (a deity). It seems no such an idea, term, or belief of Dhammapala found or developed in the Theravada traditions or in EBTs. But I could be wrong about this. Any advices? Thanks.
In Pāli, the verb pāleti means to protect or guard. So the name Dhammapāla has the sense of ‘protector of the dhamma’, or ‘dharma protector.’
Come to Sri Lanka or Thailand. Stay at some Theravāda temples. Then you’ll have a better sense of the Theravāda traditions.
Yes, folk religious practices in Theravada temples function as dhamma protector-deity.
However, in Mahayana traditions ‘dharmapala’ is within, not falling outside the doctrine of organised religion. Dharmapala - Wikipedia
Likewise in the Theravada, e.g., the Āṭānāṭiyasutta, DN32.
Utpalavarṇa (the God Viṣṇu) is traditionally considered the dharmapāla or protector of Buddhism in Śrī Laṅkā.
So, this is traditionally a folk religion of Sri Lanka.
This sutta does present the notion of a dhamma protector, but the term, dhammapala, is not presented in the text.
It seems only this text is within the teaching of Theravada traditions on the faith of dhammapala?
If so, this sutta is the earliest Buddhist text on the religious belief of ‘dhammapala’ within the doctrine of organised religion (not folk religion)?
This sutta DN32 has a Chinese counterpart T 1245: 毘沙門天王—Taishō Tripiṭaka, which is not in DA.

In the Mahayana traditions it has the traditional beliefs of Dharmapala, i.e. a dharma protector (a deity).
Could you share with us the Mahayana source you are using to make this first statement? My understanding is that this is more of an esoteric Buddhist concept found commonly among the Vajrayana traditions in Tibet as well as the Chinese esoteric Buddhist schools and Shingon in Japan.

Could you share with us the Mahayana source you are using to make this first statement?
I’ve got this idea mainly from the above-mentioned website Dharmapala - Wikipedia and its connected sources. I also noticed the Sanskrit term, dharmapala, does not have the corresponding Pali term being used; it has the corresponding Chinese/Japanese and Tibetan Buddhist terms currently being used in the related Buddhist traditions.

My understanding is that this is more of an esoteric Buddhist concept found commonly among the Vajrayana traditions in Tibet as well as the Chinese esoteric Buddhist schools and Shingon in Japan.
According to the website information and its relevant sources, almost all Mahayana and esoteric traditions/schools in Tibet, China, Japan include dharmapala beliefs.
But, as you pointed out, esoteric/Vajrayana traditions present the dharmapala faiths as one of their major religious practices.

dharmapala, does not have the corresponding Pali term being used;
As others have pointed out, dhammapala does occur in Pali, albeit rarely. So it does have a corresponding term.

it has the corresponding Chinese/Japanese and Tibetan Buddhist terms currently being used in the related Buddhist traditions.
Yes, but the majority of occurrences in Mahayana sutras prior to esoteric Buddhism becoming influential refer to people protecting the Dharma, not deities. As far as I can see, it’s a late era concept that arose, but which has since influenced most contemporary forms of Buddhism. Thus, we see dharmapala deities in art and statuary throughout the Buddhist world, but it was not an early Buddhist concept IMO. It’s very late in Buddhist history.