As stated clearly in Dhammapada 254 - 255, noble (ariya) contemplatives cannot be found outside what was taught by the Buddhas. In other words, you can only find noble contemplatives where there are the four noble truths, the noble eightfold path, the three marks of existence and dependent origination. Only these lead to the permanent end of suffering.
In the sky there is no track; outside the Buddha's Teaching
there is no ariya bhikkhu (samana). All beings take delight in fetters
(i.e., craving, pride and wrong view) that prolong samsara; all the
Buddhas are free from these fetters.
In the sky there is no track; outside the Buddha's Teaching
there is no ariya bhikkhu (samana). There is no conditioned thing that
is permanent; all the Buddhas are unperturbed (by craving, pride and
wrong view).
Dhammapada 254 - 255
Also the following sutta says that the Noble Eightfold Path is mandatory for liberation.
And the Blessed One spoke, saying: "In whatsoever Dhamma and
Discipline, Subhadda, there is not found the Noble Eightfold Path,
neither is there found a true ascetic of the first, second, third, or
fourth degree of saintliness. But in whatsoever Dhamma and Discipline
there is found the Noble Eightfold Path, there is found a true ascetic
of the first, second, third, and fourth degrees of saintliness.
Now in this Dhamma and Discipline, Subhadda, is found the Noble
Eightfold Path; and in it alone are also found true ascetics of the
first, second, third, and fourth degrees of saintliness. Devoid of
true ascetics are the systems of other teachers. But if, Subhadda, the
bhikkhus live righteously, the world will not be destitute of arahats.
DN 16
In fact, the specific person of Gautama Buddha is not more important than his teachings, which was discovered and rediscovered again by multiple Buddhas (SN 6.2) in history, as a natural law.
Past Buddhas,
future Buddhas,
& he who is the Buddha now,
removing the sorrow of many —
all have dwelt,
will dwell, he dwells,
revering the true Dhamma.
This, for Buddhas, is a natural law.
Therefore one who desires his own good,
aspiring for greatness,
should respect the true Dhamma,
recollecting the Buddhas' Teaching.
SN 6.2
Even if Buddhas never arose, the three marks of existence is in any case a natural law independent of the person discovering and teaching it (AN 3.136).
“Mendicants, whether Realized Ones arise or not, this law of nature
persists, this regularity of natural principles, this invariance of
natural principles: all conditions are impermanent. A Realized One
understands this and comprehends it, then he explains, teaches,
asserts, establishes, clarifies, analyzes, and reveals it: ‘All
conditions are impermanent.’
Whether Realized Ones arise or not, this law of nature persists, this
regularity of natural principles, this invariance of natural
principles: all conditions are suffering. A Realized One understands
this and comprehends it, then he explains, teaches, asserts,
establishes, clarifies, analyzes, and reveals it: ‘All conditions are
suffering.’
Whether Realized Ones arise or not, this law of nature persists, this
regularity of natural principles, this invariance of natural
principles: all things are not-self. A Realized One understands this
and comprehends it, then he explains, teaches, asserts, establishes,
clarifies, analyzes, and reveals it: ‘All things are not-self.’”
AN 3.136