Is it a mod compatibility issue?

Yes

If it's a mod compatibility issue, please provide the link(s) to the incompatible mod(s)

https://www.curseforge.com/minecraft/mc-mods/rubidium

Minecraft version

Other (specify below)

Describe the issue

Apparently, running the mod with Rubidium (on 1.16.5 atleast] seems to break rendering; and no blocks are visible. Specifics on whether it is a setting issue are currently unknown.

1.16 is no longer support, update to a more modern version