Can you be polyamorous without sex? Can asexual people be polyamorous?
Yes to both. Polyamory is about multiple loving romantic relationships, not about counting sexual partners. Many polyamorous people are asexual or have low sexual frequency; the romantic and emotional depth across multiple partners is the structure, not the sexual count.
Polyamory is centred on romantic and emotional depth across multiple partners, not on sexual activity. The 'amor' in the word is love, not sex. Asexual people, demisexual people, people in long sexually-low periods of life, and people who have specific sexual configurations they are not actively expanding can all be polyamorous in orientation and practice.
What polyamorous asexual practice often looks like. Multiple deep romantic relationships, with the sexual dimension handled per relationship — some sexual, some not, some sexual at one rhythm and others at another. The polyamorous structure removes the assumption that any one partner has to be the sole vessel for all romantic, emotional, and (separately) sexual needs, which can make space for asexual practitioners to have romantic depth without sexual pressure that doesn't fit them.
Common considerations specific to asexual polyamory. Partners' sexual orientations may differ from yours; the network may include some asexual and some allosexual partners; some relationships may involve sex and others may be entirely non-sexual. The standard practice is the same as in any polyamory: explicit communication about what each relationship is and isn't.
What about queerplatonic relationships. A queerplatonic relationship is a deep, committed partnership that doesn't fit the romantic-friend binary cleanly. Some asexual polyamorous practitioners have queerplatonic partners alongside romantic ones; the structure accommodates this without strain, because polyamory's premise is not 'multiple sex partners' but 'multiple committed connections of various shapes.'