How to Make default value of single line of text be read-only on in SharePoint online modern list

How to Make default value of single line of text be read-only on in SharePoint online modern list.

I have the same requirement as mention in this post and have to implement this in the modern list, any suggestion on how to achieve this.

https://sharepoint.stackexchange.com/questions/242122/make-default-value-of-single-line-of-text-be-read-only-on-new-edit-form

Thank you