WP Featured Image To Recent Posts in Sidebar... Possible ?

I'm using the free version of generatepress theme and i'm editing it to my liking.
I'm trying to add the featured image to the recent posts thats in the sidebar (widget)

Also, maybe you can tell me where can i see the html code for the sidebar (i've looked everywhere), maybe i can insert featured images this way.
Maybe i can get some pointers to how i can do this.

I dont want to use plugins ... but if you do think thats the only way to do the job, plugins are ok too ... if theyre very trustworthy i guess

can't help you with the "html code for the sidebar" part (mainly because I don't understand what you're asking), but I'm pretty sure you can add featured images in recent posts with any "recent posts" plugin that has thumbnailing capabilities... sometimes you can do this even with the theme itself, and GeneratePress is one of the best themes out there, it has to be capable of doing this

Search for "Recent Posts Widget With Thumbnails", It is a plugin but never had issues with it, and does exactly what you want.

i found the answear i was looking for ... https://developer.wordpress.org/themes/functionality/featured-images-post-thumbnails/
however, i cant seem to find the php file for the sidebar where i can insert the code shown on wordpress.org

in other words, i need the file that has for example the html tags <h1> <div>, to style the sidebar, which also uses wordpress php code to call title, url, etc

solved it ... this is something very easy to do actually in the admin page. no need to code i, no need for plugins. interestingly nowhere on the web does it say anything about it. so here's the solution for those landing here in your quest for same problem.
insert latest posts (in this example) using the widgets menu from admin. then click the related posts to select it, and then on the right side select "block". that's where you can find the "featured image settings" (somewhere lower,under post meta settings). next, selct thumbnail > 100% width ...then click update, and your done ! easy peasy