When the Lion program came out of pilot in 2018, this was the guidance at that time:
Scouting Wire: What You Need to Know About Lions Integrating with Cub Scouts
Can we register Lions for the fall now?
The Lions program starts in August or later. Councils should recruit and register Lions as close to the start time of the program and their den. There is no summer program for Lions. Youth should be recruited close to the time that councils have active programs to deliver to the youth.
Whether this was intended to be temporary guidance or not, I do not know. But the Guide to Safe Scouting seems to indicate that there is still no summer camp program for Lions.