I didn't find anything for this season, but Paris Saint-Germain had the most times offside by a club with more than 0 titles and in the Champions League in 2025-26, with 29 times offside.
PSGStatMuse has Champions League data for times offside going back to the 2015-16 season.
More PSG Stats
Team Leaders 
G
2
Torres
A
2
Ruiz
RTG
9.55
Torres
Team Rankings
GF
2
3rd
GA
2
10th
GD
0
6th
FORM
D
last 5
Lyon
Monaco
Brest
Rennes