Lens have won three matches in a row all competition from Ligue 1 until UEFA Champion League, seems excited with Lens back to the top performing in this season exactly success defeated Arsenal on Champion League match. Current standings in Ligue 1 although still in few slip above relegation zone teams but winning over Arsenal make Lens more confidence upcoming match in Ligue against against Lille.
Both domestic league and Champion League are important for Ligue 1 team, if can't performing well in domestic league and finish on Champion League spot standings I don't think how come they will participate in Champion League competition. But PSG have an exception, winning Champion League is most priority for them after failure every season and Luis Henrique could give difference result for PSG in Champion League performance.
I have a difference of opinion with you regarding domestic league matches with other competitions such as UCL. of course, this match has difference, even though the performance in the domestic league is very bad, it does not necessarily mean that the UCL match will also be bad for reasons such as Lens performing a little badly in League 1. there is possibility that only maintaining the physical quality of the players to focus on the UCL match, even though in League 1, is also very important. but there a competition that must be prioritized first. If UCL manages to secure points, of course every time there is break in the match, UCL Lens has the right to chase points in League 1 even though they have to fight hard, but if they want to get a UCL ticket in next season, Lens must immediately improve the quality their performance.