As with any major OS release, we recommend a cautious approach, especially where your primary device is concerned. Major releases often bring new issues or bugs, which may take some time for the vendor to address with patches and updates.
We have reports that Mac users who have upgraded to Catalina from a prior version of MacOS (or who have transferred data from a system using a prior version of MacOS) have experienced problems with wireless networking. In particular, users may see no wireless network SSIDs available, and users may be unable to connect to any captive portal wireless network (frequently used at public hotspots).
We expect such issues to be cleared up in a future release of Catalina.
If you have already encountered these wireless networking problems with Catalina, read on.
Dealing with no visible SSIDs to join
This seems to mostly affect those who have VPN software installed. If you are able to uninstall all VPN software before upgrading or transferring data, you might avoid this issue. It has been reported that the fix detailed here on iGeeksBlog may fix the problem (disable wifi, delete some plists, and reboot).
Dealing with inability to use a wireless captive portal
A temporary workaround is detailed here on Poweruser.Blog, which involves using a new plist file to create and start a new LaunchDaemon. This would need to be removed again, once the bug is addressed in some future MacOS update.