You already posted this question on the official product forum (https://community.softwaregrp.com/t5/LoadRunner-Practitioners-Forum/Urgent-Truclient-chrome-instance-is-opening-in-Incognito-mode/m-p/1624503) and got a response by the lead developer of the TruClient protocol.
His answer is:
TruClient runs the browser in Incognito/Privacy mode to allow separation of
Vusers during a load test.
This cannot be disabled or changed.
Perhaps you can elaborate on why your application is not working in these
modes, so we can try to find a workaround.
and then
Some browser features behave differently in privacy mode.
For example, IndexedDB cache mechanism is not implemented in Firefox
private mode [See the bug in Mozilla]
https://bugzilla.mozilla.org/show_bug.cgi?id=781982
From the error you mentioned, it seems this is related a similar browser issue.
As mentioned before, it is not possible to run TruClient in non-private mode.