We could do compulsory voting without making you choose literally anything on the ballot. If you want to protest vote, you could literally turn in an empty ballot (and honestly that’s what everyone should be doing who genuinely wants to protest vote).

"As voting is compulsory, electors are given a number of ways to cast their vote at an election, including postal voting, pre-poll voting, absent voting, voting at Australian overseas missions and voting at mobile teams at hospitals and nursing homes and in remote localities, as well as ordinary voting at a polling place in their electorate.

Because of the secrecy of the ballot, it is not possible to determine whether a person has completed their ballot paper prior to placing it in the ballot box. It is therefore not possible to determine whether all electors have met their legislated duty to vote. It is, however, possible to determine that an elector has attended a polling place or mobile polling team (or applied for a postal vote, pre-poll vote or absent vote) and been issued with a ballot paper."

https://www.aec.gov.au/about_aec/publications/voting/

If you're that desperate to prove you're the purest Anarchist you can just turn in an empty ballot. Or it's a $20 fine for noncompliance. Or you could, you know, participate in democracy. Authoritarians generally don't like it when people vote.

You should do some more reading then because it's not. It's for preventing systemic apathy.

Still sounds like authoritarianism to me. If we are going full authoritarians, then I’d rather prevent so many people from voting.