Unfortunately there is no perfect alternative to ChemDraw in terms of convenience and functionality. One possible option is ACD ChemSketch, which is a decent software for most structure drawing needs. I also used in the past ISIS Draw (from MDL); it is not supported now, but you can still find an old version on the Internet and download it. If you are OK with using web based structure editor, consider Marvin (used for drawing structures in Reaxys).
Google search shows many others, but I did not use anything except for the ones mentioned above, so I cannot comment on them.
Biovia DRAW 16 is free and comparable by functionality. Available in ver. 18 from https://discover.3ds.com/biovia-draw-academic.
Interface is not very convenient, but Biovia DRAW 16 have IUPAC name generator without size restriction, a highly valuable feature that is available only in cutted version in ChemDraw.
I have also distributives of minor used programms like ChemWin6, ChemDoodle and ChemSketch (in addition to mentioned ones by https://www.researchgate.net/profile/Vladimir-Khlebnikov ), but RG do not accept upload in public site.
For Android smartphone you would install KETCHER - to fix brilliant ideas in anywhere )))
Your post reminded me of the story of ISISDraw after MDL went out of business: for some time it has renamed to Symyx Draw, then it was acquired by Accelrys, and eventually become known as BIOVIA, now owned by Dassault Systems.