How does a chess rating at Lichess.org compare against a rating in real life, in classic chess (more than 8 min)?
The largest problem with sites like LiChess and Chess.com is that the standard pools are not very reflective of Over The Board rating. Most people play chess online for the Blitz and Lightning games. Chess.com recently came out with some statistics that showed that their Blitz rating pool is roughly the same as USCF currently. I do not know how well that would translate for the Standard pools.
When I was 1900 playing G/30 games on Chess.com and ICC (Internet Chess Club), I was rating roughly 2100/2200 on both sites. This was years ago though, so again, not entirely sure how accurate they are.
My real life rating is higher than all my online ratings. This could be because I'm more serious in real life tournaments and calculate much deeper into positions than I do in online chess. It could also be I'm worse at faster games. I know my highest online ratings tend to be longer time controls.
Fast chess favors opening knowledge, quick solid play while looking for tactical opportunitues, and good endgame knowledge. Otb tournaments favor objectively best moves in general, as well as being able to set up positions that are complex enough your opponent can't accurately evaluate them.