It seems to work 🙂
I added Font ULR with a weird ending ?ka575c <link rel="preload" href="https://www.sisla.lt/wp-content/plugins/wp-show-posts-pro/fonts/wp-show-posts.ttf?ka575c" as="font" crossorigin="anonymous">
If not added: ?ka575c
Google PageSpeed Insights test result:
Warnings: Lighthouse was unable to automatically check the font-display value for the origin https://www.sisla.lt.