Try making the overly broad permissions of /etc/mysql/ssl/server-key.pem -rwxr-xr-x to something less world-readable.
- Bug#927289: mariadb-server-10.3: SSL error: Unable to ge... Olaf van der Spek
- Bug#927289: [debian-mysql] Bug#927289: mariadb-serv... Otto Kekäläinen
- Bug#927289: [debian-mysql] Bug#927289: mariadb-... Olaf van der Spek
- Bug#927289: [debian-mysql] Bug#927289: mari... Otto Kekäläinen
- Bug#927289: [debian-mysql] Bug#927289: ... Olaf van der Spek
- Bug#927289: [debian-mysql] Bug#927... Otto Kekäläinen
- Bug#927289: [debian-mysql] Bug... Olaf van der Spek