Hi @Usman!
Thanks for the additional info.
Please keep in mind that newer releases are not only important to have access to newer features and better/up-to-date implementations, but also to have a more secure device since new bugs are found and fixed constantly. Continuing using old software (e.g. Linux Kernel itself) can be seen a making your system more vulnerable to known bugs/attacks.
Therefore the recommendation is to bring your system to a reasonably up-to-date release.
Regarding the dual display setup, I found this old thread where a possible set of kernel arguments is shared. Have you tried like this?
Also, in the link you shared (Display Output, Resolution and Timings (Linux) | Toradex Developer Center) it states:
[…] one might have to tweak the framebuffer timings or adapt the kernel sources to use different clock parents for the different framebuffers. The clock tree in
/sys/kernel/debug/clk/clk_summarycan be used to debug the issue.
Have you looked into this?
Best regards,