Is there any evidence that this phrase should be translated 'ganja'?
Exodus 30:23 (ESV) reads:
Take the finest spices: of liquid myrrh 500 shekels, and of sweet-smelling cinnamon half as much, that is, 250, and 250 of aromatic cane (qənêh-bōśem)
The OP points out:
there is a speculation that kaneh bosem is a plural form of kaneh bos.
This is based, presumably, on a misunderstanding of the ending
em on bōśem. This is superficially similar to the masculine plural -ı̂m ending in Hebrew. However, the term qənêh-bōśem is singular (i.e. 250 shekels-worth of q-). The letter
m is part of the root bśm.1 The word qənêh- (spelled qāneh when alone) is a common term for "cane" or "reed". The phrase, then, is literally "cane of spice". The second noun bōśem is taken attributively, hence "fragrant cane". "Bos" means nothing in this context.2
As for the actual plant referred to in Exodus, I will believe William Propp's account:
fragrant cane. Qənē(h) bōśem is also called qāne(h) haṭṭôb ‘the sweet cane’ (Jer 6:20; cf. Akkadian qanû ṭābu) and simply qāne(h) 'cane' (Isa 43:24; Ezek 27:19). Although reeds are found in Israel itself, it is clear from the prophets that this special cane, like frankincense, was imported "from a distant land." Of various grasses valued in Antiquity for their aromatic essences...the variety most familiar to my readers will be East Asian "lemongrass."
Propp equates the terms bōśem and beśem earlier in the verse (there constructed with "cinnamon"). The emphasis is on their fragrance; there is no evidence of psychedelic properties attributed these plants in the Exodus account.
1. Were it plural, it would be bəśāmı̂m.
2. The etymologically related botanical term is is not cannabis but balsam.