i really like tixati and would use it instead of qbittorrent if tixati has sequential download feature. but i'm arch user so i would like to see source code to install newest versions from aur or compile it by myself. should i check it from time to time or tixati will never be open source?

tixati does have a sequential download function, right click a file and look in the menu, it's in there

Yes it is there but you really should not use it unless your only peers are seeds. It totally f**** the other leeches in a download. Only use if you must, never use it for convenience