Ospreys were no match for Saracens on Saturday, while Exeter Chiefs were among the other European Champions Cup winners.
Danny Wilson will replace Dave Rennie when the Glasgow Warriors head coach takes the Australia job.
Ireland centre Garry Ringrose was the star of the show as Leinster started their bid to regain the Champions Cup with a bonus-point win.
Munster were delighted to have Andrew Conway back in Pro14 action as he settled an all-Irish affair with Ulster.
Undefeated Leinster made light work of the Dragons as Glasgow Warriors thrashed Southern Kings 50-0 on Friday.
The standout team in Pro14 could only manage a 3-0 win against winless Zebre as Leinster struggled on Saturday.
Scarlets made it three from three in Pro14 on Sunday as Glasgow Warriors earned a first win of the season.
Leinster's 21-year-old hooker Ronan Kelleher ran in a hat-trick in their thrashing of the Ospreys, while the Scarlets saw held off Glasgow.
Ruan Pienaar inspired the Cheetahs to victory over the Glasgow Warriors on Friday, while Ulster were too good for the Ospreys.
Munster, Racing 92 and the Ospreys will take on holders Saracens in the pool stage of the 2019-20 European Champions Cup.
Leinster failed to read the script as Stuart Hogg's final Glasgow Warriors match ended in a painful Pro14 final defeat.
Tommy Seymour scored two of his team's seven tries as Glasgow Warriors routed Ulster in the first Pro14 semi-final.
Exeter Chiefs-bound Scotland full-back Stuart Hogg knows Glasgow Warriors will have to be at their best to see off Ulster.
A dramatic final day of the regular season in the Pro14 saw Glasgow Warriors make the semi-finals, while Ospreys and Scarlets will face off.
Glasgow Warriors celebrated the news that head coach Dave Rennie will stay at the club by securing a famous win over Leinster in Dublin.
Dave Rennie has been linked with the Australia job, but the New Zealander will spend at least one more season with Glasgow.