Start by choosing a network, try something like Libera Chat https://libera.chat/

You have some suggestions for IRC clients on their page, you can even use one on the browser. Browse the channels available, join, chat

Hosted or client, there’s IRC clients for everything, even on a Commodore 64 (https://csdb.dk/release/?id=197138)

I don’t use it for a longtime, but if it works why change it. It good for realtime chat, you can use it on a potato and some. Matrix chats also have IRC bridges so all can be on same chat.

There are some desktop apps https://lemdro.id/post/4319

Blink is a fork of WebKit wich is a fork of KHTML, KHTML exist since the '98, the codebase isn’t that younger too. Was tweaked by Apple then by Google, with some features that don’t exist on other engines.

Some apps already support videos, like Voyager, Liftoff and Lemmy on desktop.

You just need to share the file on external service like catbox.moe

There’s already some communities for video only like !combatfootage@lemmy.world

On mobile you can use Voyager as webapp (https://vger.app), for desktop you can use the LemmyTools to auto-expand images (https://github.com/howdy-tsc/LemmyTools).

There’s also other 3rd party apps that you can use https://lemmyapps.netlify.app/

some instances already include Voyager on their service (m.lemdro.id, m.lemmy.world)