I haven't tried this. Possibilities are renaming the base directory, install beta, rename it and then rename base back, using a docker container, install as second user with no system privileges, virtual machine, Ubuntu on a stick, etc. Alternatively, skip and go naked. Set up with RStudio cloud and install \beta over existing, having first taken the usual precautions.
Those may involve more bother than the warnings. I'd go save everything-uninstall with apt remove, reinstall from the deb with Eddy or some such. Test. If it works, stay there until out-of-\beta. That's what I'd do if so motivated.
(I have a generic face--I'm someone's uncle wherever I go, people accost me on the streets of foreign cities confident that I can tell them in their native language where the post office is. Should have been a spook, I guess.)