In most countries, including in Europe, the H.264 patents have already expired. There you can use H.264 freely.

Some patents remain valid in USA, Brazil and a few other countries.

This is for patent licensing. Using an open source implementation doesn't get rid of your obligation to license the patents for it.

VP9, AV1

AV1, as well as the older On2 codec series it was based off of (VP9, VP8, etc).