Verified in Satellite 6.5.3 Snap 1
On a satellite with over 10k hosts and more than 250 registered through insights, both the overview and inventory pages loaded without any issues (albeit slightly slower).
See attached recording for verification.
Created attachment 1626127 [details]
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.