With the most recent Gmail UI, the menu item has changed to an icon which you never would guess toggled highlighting until you actually hover over it to get the help text. It's in the top-right corner next to the printer icon.
Gmail has user created labels and system labels. inbox is one of the system labels.
To search for email with
user created labels use: has:userlabels
user created labels or inbox label use: has:userlabels | in:inbox
Search operators you can use with Gmail - Gmail Help
A Google representative confirmed this feature was discontinued in late 2020:
That bar is only an email search bar now. It no longer does web searches, nor finds Contacts, Drive files, nor anything else. -tony_b (Platinum Product Expert)
Because Gmail interprets searches for something, that looks like a number, as a search for that number, and searches for strings as searches for complete words.
Accordingly, your search for '192.168' is interpreted as a search for the number 192 decimal point 168.
And your search for '192.168.100.150' is interpreted as a search for the word '192.168.100.150'....