Sorry you are having issues, but I can say for certain CentOS runs fine on a DL20 Gen10
[root@sandbox ~]# cat /etc/centos-release
CentOS Linux release 7.6.1810 (Core)
[root@sandbox ~]# dmidecode -t 1
# dmidecode 3.1
Getting SMBIOS data from sysfs.
SMBIOS 3.1.1 present.
Handle 0x001C, DMI type 1, 27 bytes
System Information
Manufacturer: HPE
Product Name: ProLiant DL20 Gen10
Version: Not Specified
Serial Number: H I D D E N
UUID: 30324c44-4143-4e43-3638-12345678911
Wake-up Type: Power Switch
SKU Number: DL20GEN10
Family: ProLiant
You need to disable the S100i controller RAID mode and set it to SATA AHCI