Legacy PCs
Legacy PCs can play through a Java applet, but the code is unsigned so some changes have to be made.
First, install Java 5. Then edit your policy file (article was intended for 4 but applies):
https://itspazaz.com/2023-10-12-java4-policy/
Java 5 Runtime:
https://runewiki.org/archive/misc/jre-1_5_0_22-windows-i586-p.exe