Here’s an update for anyone who decides to go down this 
rocky route:
Numerous tests and attempts were made. I’m not a total noob when it comes to Linux, webmin, and Virtualmin, but it really took plenty of effort to get to the conclusions:
+----------+---------+-----------------------------------------------------+
| OS | MySQL | Comment |
+----------+---------+-----------------------------------------------------+
| CentOS 8 | Ver 8 | Possible compatibility issues in other components***|
+----------+---------+-----------------------------------------------------+
| CentOS 8 | Ver 5.7 | MySQL 5.7 is not available for CentOS 8 |
+----------+---------+-----------------------------------------------------+
| CentOS 7 | Ver 5.7 | Removal of MariaDB* causes chroot to fail |
+----------+---------+-----------------------------------------------------+
| CentOS 7 | Ver 5.7 | As a Remote DB Server, it randomly denies service** |
+----------+---------+-----------------------------------------------------+
* Speculation: When MariaDB gets uninstalled some components and their settings files get removed. Reinstallation of these components didn’t help. Chroot’s problem manifested by closing SSH connections immediately after connecting. (Also there seems to be a bug with chroot and Virtualmin on CentsOS 8, but that’s another thing). Other uncovered issues might also exist, but I preferred not to continue on this path.
** The remote connections to MySQL were sketchy, to say the least. Every so often, out of the blue, the connection would fail, and the error message coming from MySQL was not helpful at all, claiming that the connecting user does not have permission, although the same connection and action was just being done a minute ago and it was working fine. So frustrating!
*** Amnesia… I no longer remember accurately why it didn’t work. Possibly because it was my first attempt and I didn’t have any experience with MySQL.
So what did I do eventually you may ask…
Well, I had an old installation of Vesta Control Panel on one of the servers. Vesta comes with MySQL, and that’s what they got to get eventually.