I haven't followed the curling mixed doubles competition, but below is an overview of qualification scenarios. Hopefully, I haven't made any mistakes.
Group A
This is the only group with no-mathematically-qualified teams yet and the only group with four teams still in contention. Remaining matches are Czechia-South Korea, which will be played first and Canada-Great Britain. If you don't want to get confused with text, jump directly to the tables.
If Czechia wins, then they qualify and they will be joined by the winner of the other match. If it's Great Britain, then GB wins the group and Czechia finishes second. If it's Canada, then Czechia wins the group and Canada ends up second.
To summarise, if Czechia wins.
Winner of -
/ Group Standings
1
2
If South Korea wins, then the winner of Great Britain-Canada certainly wins the group.
If Great Britain loses that match, a three way tie between Czechia, Great Britain and South Korea will be created. In this case, South Korea will win the tie with a 2-0 win-loss record in the tie-breaker.
If Canada loses that match, a three way tie between Canada, Czechia and South Korea will be created. Win-loss record for all tied teams will be 1-1. In that case qualification will be decided based on draw shot challenge. At the moment, it's South Korea (43.46) ahead of Czechia (48.09) ahead of Canada (59.66).
To summarise, if South Korea wins.
Winner of -
/ Group Standings
1
2
DSC (,,)
Group B
USA and Sweden have both secured their spots in the quarterfinals. US team is undefeated and still has one match to play. They are certainly first as they have won against Sweden, who completed the group with a 4-1 win-loss record.
Group C
China is the group winner as they are undefeated with one match to play and they have won against Japan and Latvia, both of them having a 3-1 win-loss record. These two teams are facing each other tomorrow, therefore whoever wins gets the second spot.
Group D
Both teams in the current top two, Germany and Switzerland, have completed their matches and they both have a 4-1 win-loss record. However, as I'll explain thoroughly, only Germany is mathematically qualified. Denmark is in third place with a 3-1 win-loss record and will face Kazakhstan tomorrow.
Obviously, if Denmark loses, then Germany and Switzerland are through to the quarterfinals, with the former winning the group, having won the direct match up.
If Denmark wins, then a three way tie at a 4-1 win-loss record will be created. In this case, the tie-breaker win-loss record will be 1-1 for all three teams and qualification will come down to draw shot challenge. But as I mentioned above, Germany and Switzerland have completed their matches, which means their current DSC is their final one. Since Germany (31.04) is better than Switzerland (79.90), Germany will definitely finish ahead of Switzerland in this tie. Given that Denmark's current DSC is 37.31, at the moment they also have the upper hand against Switzerland in this scenario.