Hi!
The same problem is happening to us. Updates 14.9 and 15.0 broke Elementor, causing the server error (500 error).
However, version 14.8 works correctly.
Our settings:
WP Version: 5.5.1
PHP Memory Limit: 2 GB
WP Memory Limit: 40 MB
Number of Category: 75
Number of Tag: 7415
PHP Version: 7.4.8
PHP Post Max Size: 1 GB
PHP Time Limit: 3000
PHP Max Input Vars: 5000