On December 2, the Maine Secretary of State released new registration data. See it here. The state totals are: Democratic 399,135; Republican 315,907; independent 361,602; Green 45,578; Libertarian 254; People’s 41.
Percentages are: 35.56%; Republican 28.14%; independent and other 32.21%; Green 4.06%; Libertarian .02%; People’s .00+.
Percentages in November 2020 were: Democratic 35.68%; Republican 28.36%; independent and other 31.94%; Green 4.01%; Libertarian .00+.
The reason the Libertarian registration is so low is that the state converted all registered Libertarians to independents in early 2019.
The December 1, 2021 print issue of Ballot Access News has a registration chart showing the number of voters in each party, in each state. However that issue went to press before the new Maine data was available.