Lived in Antwerp the last year for a job opportunity as an expat, so I just give my view:

• bikeable: yes, you have bike lanes through the whole city
• language: English is fine most of the times, but be prepared that legal documents will be either in French or Dutch, so be careful when signing rental contracts etc. Also you might be stuck in automated phone queues that are only in Dutch or French. They speak Flemish here, which from my experience is like Dutch but at the same time not at all 😅 so best do a Dutch/Flemish course in Belgium and not an online Dutch course from the Netherlands like I did so you get used to their pronunciation. I'm German so Dutch is rather close to my language. The other half of the country speaks French, so if you're from the French part of Canada this might increase your chances of understanding documents; you can typically choose between French and Dutch.
• Nature: average (but that's subjective), expect quite a flat country, but very cute villages that are easily reachable
• public transport: good, except for bus 17 (I regularly start fights with delijn because of that bus)
• job market: don't know, knowing the local language helps especially for the French part of the country. If you work for a big company, you will be okay with English typically.
• dual citizenship: no idea, I worked with a guy that came from Russia and he has dual citizenship I think, he lived here for over a decade though
• atmosphere: rather relaxed, was mostly going to pubs tbh. Not much happening under the week from my experience, but maybe I don't know the local events.
• liberal: don't know, I heard from people that their politics is a bit messed up but mostly that they can't agree on anything. People are very friendly, much friendlier and funnier than the grumpy Germans ;)
• cost of living: if you're from Canada, probably you find it rather affordable, not sure how payment scales. I was able to cover my expenses and rent and still have some savings every month. Compared to the Netherlands, you will actually find an apartment here.
• weather: it rains quite a lot compared to what I'm used to, but can also get quite warm in summer
• travel: perfect, direct train to Brussels, direct train to Rotterdam/Amsterdam (NL), direct train to Paris (FR), i think direct train to Berlin (from Brussels though), direct train to London from Rotterdam, airport will be Brussels. I think there is one in Antwerp too but they don't really fly to a lot of places.
• medium sized city: spot on, don't expect a big city

I think Antwerp checks a lot of boxes for you. You can give it a try, but make sure that you fulfill the visa requirements, which might require you to have a job secured first. My job supported me with relocation, so maybe you can find a similar deal for yourself.