See here:
https://github.com/twbs/bootstrap/blob/main/scss/_variables.scss#LL804C1-L804C24
$input-btn-border-width is now a custom variable.
(see bootstrap 5.2 version: https://github.com/twbs/bootstrap/blob/v5.2.3/scss/_variables.scss#L738 where $input-btn-border-width was a simple scss variable)
The main problem is that on file:
@progress\kendo-theme-bootstrap\scss\input\_variables.scss you are using:
$kendo-input-border-width: $input-border-width !default;
$kendo-input-border-height: ( $kendo-input-border-width * 2 ) !default;
so scss compilation gives me an error:
SassError: Undefined operation "var(--bs-border-width) * 2". ╷ 10 │ $kendo-input-border-height: ( $kendo-input-border-width * 2 ) !default;
My temporary fix is to define, before importing _variables file:
$kendo-input-border-width: 1px !default;
Basically, the main problem is that package @progress/kendo-theme-bootstrap 6.4.0 with bootstrap 5.3 doesn't work anymore.
Thanks.
Diego