Indeed. the Tibetans and Chinese have used their own languages for centuries, and there’s nothing wrong with that.
Also a good point. If we insist that the exact pronunciation of Pali is essential for valid ordination, it’s possible that even the first generations of students had invalid ordination.
Imagine getting in the Tardis and going back to the hills of Magadha 2500 years ago, and attending an ordination. There they all are, Sāriputta as preceptor, and around all the great monks. So inspiring! The appointed monk begins the recitation.
sunātu me bhaṁte saṁghe
You look around. Hello! Does no-one see the problem? Sure of yourself, you clear your throat and say, “Ahh, excuse me gentlemen, it’s saṅgho.”
Their response:

No, not always. In Thailand I’ve never heard of it, at least in the forest tradition everyone just chants normally, there’s no training or expectation as to pronunciation at all. In Sri Lanka, some Nikayas will recite twice, with niggahita pronounced as m and ng. Just to be sure!
The best guide for this is, in my view, in Parajika 1, where the language of disrobal is discussed. Clearly the intent of the whole passage is that it is comprehension that matters. Surely the same principle should apply for ordination.
https://suttacentral.net/pli-tv-bu-vb-pj1/en/brahmali
If you renounce the training in an Indo-Aryan language to a non-Indo-Aryan speaker who doesn’t understand you, the training isn’t renounced.
Ariyakena milakkhassa santike sikkhaṁ paccakkhāti, so ca na paṭivijānāti, apaccakkhātā hoti sikkhā.
If you renounce the training in a non-Indo-Aryan language to an Indo-Aryan speaker who doesn’t understand you, the training isn’t renounced.
Milakkhakena ariyassa santike sikkhaṁ paccakkhāti, so ca na paṭivijānāti, apaccakkhātā hoti sikkhā.
If you renounce the training in an Indo-Aryan language to an Indo-Aryan speaker who doesn’t understand you, the training isn’t renounced.
Ariyakena ariyassa santike sikkhaṁ paccakkhāti, so ca na paṭivijānāti, apaccakkhātā hoti sikkhā.
If you renounce the training in a non-Indo-Aryan language to a non-Indo-Aryan speaker who doesn’t understand you, the training isn’t renounced.
Milakkhakena milakkhassa santike sikkhaṁ paccakkhāti, so ca na paṭivijānāti, apaccakkhātā hoti sikkhā.
Brahmali uses “Indian” and “foreign” for ariyaka and milakkha, but I disagree. Milakkha refers to Indian people using non Indo-Aryan languages, such as Dravidian or Munda, etc. If anything, the Indo-Aryans were foreigners (although they had already arrived centuries before.)
One interesting implication of this is that it confirms that not all members of the early Sangha spoke Indo-Aryan languages, at least not natively.