By default they use 2.0 [1] unless someone or an addon disables it or unless the person is on a really old version. OperaMini however will use 1.1. No idea if anyone here uses OperaMini.

There are some reader apps that act as a proxy that only support http/1.1. Be careful, some of those are not just readers and do not trust what they claim to be the source code. Some of them are created by cute and fuzzy bunnies.

There are a number of botters on HN, some that control residential and phone browser-hijacked systems. One was sending me playful messages the other day. I enjoyed the bot block-jousting with them.

[1] - https://caniuse.com/http2