You can have either connman or network manager. The packages are mutually exclusive.

Error /net/connman/technology/wifi: No carrier
You have enabled your wifi with:

$ connmanctl enable wifi

If wireless scanning leads to above error, this may be due to an unresolved bug. If it does not resolve even though wireless preconditions[dead link 2023-09-16 ⓘ] are met, try again after disabling competing network managers and rebooting.

This may also simply be caused by the wireless interface being blocked by rfkill, which can occur after restarting wpa_supplicant. Use rfkill list to check.

The best however is to not use any of those configuration scramblers, but to settle for the original ifupdown system together with wpagui. With those you are seated with maximal flexibility, simple configuration basis by editing text file(s) and a fantastic opportunity catering for any custom networking landscaping.

All it takes is a bit of knowledge which is acquired by means of reading -- reading man pages, starting with man interfaces. Knowledge is power. When you give knowledge away for an idea of convenience, then you lose.