First time poster here, so apologies if this is a silly question.
Just returned an LG (webOS) TV and got a Phillips (Android). With the LG it was easy to stream my Pc (and mobile) screen to the TV. Can I do something g similar with Android? (I thought that it had Chrome cast built in, but maybe it hasn't...)
Yes you can. The TV indeed has Chromecast built-in.
For casting from PC, use Chrome or Edge browser.
For phone, it's app specific.