Yeah, I’m currently seeing:
Fatal error: Array and string offset access syntax with curly braces is no longer supported in /wp-content/plugins/dk-pdf/vendor/mpdf/mpdf/src/Mpdf.php on line 2209
on PHP 8.0.x when trying to view the generated PDF with the current version. It seems the mPDF library that’s bundled with this plugin needs to be updated.
I agree with @djw0510, @lusant should look to propose things at https://github.com/Dinamiko/dk-pdf to accommodate and help make sure this is updated sooner than later (with the WP.org version not seeing an update in over a year & the code itself, according to GitHub, possibly being older than that so an extra nudge [as well as offering a patch as a public PR] is probably helpful.)
Was there anything outside of updating the mPDF library that was needed to be done in your fix, @lusant?