Hello! The status at http://crossqa.debian.net/src/mariadb-10.5 looks now with mariadb-10.5 release 1:10.5.5-3 much better than before.
Thanks for your help! If you have further improvement suggestions regarding cross-building or multiarch issues, please let me know by email or submit Merge Request directly at https://salsa.debian.org/mariadb-team/mariadb-10.5