Starting with MariaDB 10.4 (released in June 2019), you can use the OR
keyword with IDENTIFIED VIA
to allow any-of several authentication methods:
CREATE OR ALTER USER `minecraft`
IDENTIFIED VIA unix_socket
OR mysql_native_password USING PASSWORD("s3cr3tpasswvrd");
Even if your OS vendor kinda sucks at providing updates, MariaDB provides an official repository serving at least this version to distributions as old as Ubuntu 14.04, CentOS & RHEL 6, Debian 7, and Fedora 28 (all of which are already EOL), as well as up to current releases of each; this is by no means a "new, shiny, unsupported syntax feature". (For some of these [e.g. Fedora < 32], the URL isn't publicly listed, but it still exists.)