I cannot type letter ‘ç’ a with English (US, alt. Intl.)

I cannot type letter ‘ç’ (’+c) with English (US, alt. Intl.) keyboard, the letter ‘ć’ coming out instead. Its working fine before I upgrade the systems weeks ago. I try to change the keyboard layout but I can't find a layout with ‘ç’ by compose (’+c), my keyboard and my system are English(US).

In the US International keyboard, you can type "ç" by hitting Alt Gr+,. Alt Gr is your right Alt key.

The Alt Gr key hides a lot of international characters: combined with c it delivers the copyright symbol: ©.

As you discovered, the dead keys, i.e. `, ~, ' and " deliver accents on letters.

with the Compose key set and with an English (UK) keyboard, pressing Compose then c then , (comma) in succession creates the cedilla character ç.

Note that the 3 key presses "latch" (i.e. you don't need to hold the keys) so there is no need for finger Olympics in order to achieve the successive key presses.