Browscap is a PHP extension but is not part of the standard PHP extensions.
So to be clear, this issue is not related to InvoicePlane, but to your environment setup.
To analyse the issue:
you seem to have (some time ago) installed the PHP extension “browscap” and then (most probably) deleted it in the system but not removed it in the PHP.ini’s.
To solve the problem do this:
Check your php.ini for a line like this:
browscap = extra/browscap.ini
If you don’t use it, comment that line by using a ‘;’:
;browscap = extra/browscap.ini
Or install the browscap extension again to ensure the link from the PHP.ini is working fine.
Also: this will not affect the any functionallitys from InvoicePlane.