By default, Apex turns all Parent entries in a Breadcrumb into a link - even if you set the Target option of the Parent Entry to 'No Target'.
I expected the 'No Target' to be enough to remove the "a href" link, but alas.

This link of the Parent Entry can be removed by a Dynamic Action.
A bit of JavaScript changes the "a href" to a "span", recreating/preserving the original class and text.
I got the idea here: https://stackoverflow.com/questions/65833588/oracle-apex-create-read-only-breadcrumb-entry but I changed it a bit to make it more universal.

The two example Breadcrumbs A and B are basically the same, except that Breadcrumb B is changed by the Dynamic Action.
Hover over the two Parent Entries in the Breadcrumbs above to see the difference.

The resulting html for the two breadcrumbs looks like this:

<div class="t-BreadcrumbRegion-breadcrumb"> <ul class="t-Breadcrumb lto16031215392156085_1"> <li class="t-Breadcrumb-item"><a href="" class="t-Breadcrumb-label">Parent Entry A</a></li> <li class="t-Breadcrumb-item is-active" aria-current="page"> <h1 class="t-Breadcrumb-label">Child Entry A</h1> </li> </ul> </div> <div class="t-BreadcrumbRegion-breadcrumb"> <ul class="t-Breadcrumb lto8416322401106028_1"> <li class="t-Breadcrumb-item"><span class="t-Breadcrumb-label">Parent Entry B</span></li> <li class="t-Breadcrumb-item is-active" aria-current="page"> <h1 class="t-Breadcrumb-label">Child Entry B</h1> </li> </ul> </div>

Region

Identification
	Sequence	10
	Title	Breadcrumb A
	Type	Breadcrumb
Source
	Breadcrumb	Breadcrumb 1196 A

Region

Identification
	Sequence	20
	Title	Breadcrumb B
	Type	Breadcrumb
Source
	Breadcrumb	Breadcrumb 1196 B

Breadcrumb

Breadcrumb
	Name	Breadcrumb 1196 A
Breadcrumb Entry
	Page	1
	Short Name	Parent Entry A

Breadcrumb

Breadcrumb
	Name	Breadcrumb 1196 A
Breadcrumb Entry
	Page	1196
	Parent Entry	Parent Entry A
	Short Name	Child Entry A
Target
	URL	f?p=&APP_ID.:1196:&SESSION.::&DEBUG.:::

Breadcrumb

Breadcrumb
	Name	Breadcrumb 1196 B
Breadcrumb Entry
	Page	1
	Short Name	Parent Entry B

Breadcrumb

Breadcrumb
	Name	Breadcrumb 1196 B
Breadcrumb Entry
	Page	1196
	Parent Entry	Parent Entry B
	Short Name	Child Entry B
Target
	URL	f?p=&APP_ID.:1196:&SESSION.::&DEBUG.:::

Dynamic Action

Identification
	Name	Remove link from Breadcrumb Parent Entry B
Execution Options
	Sequence	10
When
	Event	Page Load
Advanced
	Event Scope	Static
True Action
Identification
	Action	Execute JavaScript Code
Settings
	Code	var bc_short_name = 'Parent Entry B'; var bc_a_html = $('a.t-Breadcrumb-label').filter(function(){ return this.innerHTML == bc_short_name; }).parent(); bc_a_html.html('<span class="t-Breadcrumb-label">' + bc_short_name + '</span>');
Execution Options
	Sequence	10
	Fire On Initialization	No