How will BTC, ETC, or QTUM investments work with the changer contract? Will they be converted to eth after the raise?
Metronome will be deployed to EVM-compatible blockchains.
Thus, Metronome on ETH will have ETH/MTN changer, and users participate in the auctions by sending ETH. The Proceeds contract stores ETH. Metronome on ETC will have ETC/MTN changer, and users participate in the auctions by sending ETC. The Proceeds contract stores ETC.
RSK, presumably pegged to BTC, would be a way to send "BTC" to Metronome, and the Proceeds contract collects RSK (BTC).
So, no conversion. The blockchain native currency is the one used in the auctions for a given chain.