I tried rallly.co, but it doesn’t allow to specify whole weekends, nor does it allow to indicate “maybe’s” (so we could as well use a poll directly in the forum here). I signed up for the mailing list about the ‘new version’, though I don’t have high expectations (last update was in 2018).
On framadate.org you also can’t set date-ranges, but that’s acceptable. It’s however a pain to add a large range of dates, and not convenient to fill in, with horizontal scrolling (copied from doodle, which is also a pain - what is the benefit of horizontal scrolling?!?).
And I used cally.com, which is the English version of the dutch datumprikker.nl which I find most convenient. Not open source, but at least GDPR-friendlier than Doodle (and without the annoying horizontal scrolling).
So, now I have three polls, of which I’ll share only one link
Hope that’s acceptable to everyone
EDIT: I see you have to leave your email address after filling in the data. If you don’t want that, feel free to leave an address from 10minutemail.com (though you wouldn’t be able to update your response) or keunes+APpoll+[your username]@mailbox.org if you want to be able to update your reply later (I can then forward any codes necessary).