I note that `rvm: jruby` gave me jruby-head it seems, 9.3.0.0,  see

openjdk version "1.8.0_191"
OpenJDK Runtime Environment (build 1.8.0_191-8u191-b12-2ubuntu0.16.04.1-b12)
OpenJDK 64-Bit Server VM (build 25.191-b12, mixed mode)
$ javac -J-Xmx32m -version
javac 1.8.0_191
$ ruby --version
jruby 9.3.0.0-SNAPSHOT (2.6.5) 2020-05-11 3b9b41e228 OpenJDK 64-Bit Server VM 25.191-b12 on 1.8.0_191-8u191-b12-2ubuntu0.16.04.1-b12 +jit [linux-x86_64]
$ rvm --version
rvm 1.29.7 (latest) by Michal Papis, Piotr Kuczynski, Wayne E. Seguin [https://rvm.io]
$ bundle --version
Bundler version 2.1.4
$ gem --version
3.0.6