I'll repeat my comment from nearly seven months ago [1] since it left a really bad taste about how users are dealt with. Nearly a year ago when the initial waves of the pandemic were raging on, Migadu removed its free tier. That's not a problem by itself because businesses have to make money to sustain and grow. But Migadu gave one month’s notice (contrary to the claims in the replies, that's what I saw) for users to switch. The replies to the comment also said that the new lowest paid tier was "affordable in every corner of the planet", which sounded quite ignorant even for a non-pandemic time.
Another point, which may matter to some people, is that while Migadu may be a Swiss company, the data centers where the mails are hosted were in France (this was the case at least a year ago). So the situation is somewhat comparable (not entirely though) to Fastmail being an Australian company with data centers in the U.S. being used.
For those who want multi-domain email services for a lower (flat) price, look at mxroute. It's based out of the U.S. though, which may not be an option for people who want certain services outside Five Eyes jurisdictions.