We have used Widget Logic (plugin) to display WordPress widgets on page(s) and or categories of our choosing using the WordPress conditional tags. For example would create side widget to a page using code like is_page (‘100’) to add a particular sidebar widget on the page with the ID of 100.
WordPress 5.8.1 switches the look of widgets from what is now called the classic widget look to the widget block editor; similar to the post and page block editor. Most of our WordPress sites have classic editor as the default choice. The block widget editor does not display any conditionals created with Widget Logic.
We have found a plugin called Widget Options that will allow the use of conditionals with your widgets and use the classic widget interface.