There is no minimum, you can contribute whatever amount you want. The calculaations on the site are just examples.
What is the advantage/s of this platform compared to Electroneum that has also the capability to mine on a mobile phone?
Platform? Envion is a security token that is eligible to receive weekly dividends paid out in ETH. Containers (MMUs) mine BTC and ETH that you receive as dividends (75% directly to token holders and 25% is reinvested to buy more mining hardware that will rise future dividend payout you will get). The conservative estimate of your investment is 161% per year.
I don't think you will ever be able to mine on your phone that ROI or even 1 ETH in short term either. Furthermore your phone will be faster dead after mining the whole time.