This doesn't address everything, but I thought I'd chime on specifically on the chat history question. It's still early days for support from most IRCd's, but IRCv3 has been slowly bringing protocol level support for many of the same features that Slack, Teams (chat), Mattermost, etc. have, including chat history support. It's likely not reasonable for the public IRC networks to ever support history, but for a self hosted IRC server to service your team/company/community/whatever, it would be totally feasible to connect and receive scrollback.